Supersonic venturi scrubber for containment filtration and discharge system

Abstract

The invention provides a supersonic venturi scrubber for a containment filtration and discharge system, and belongs to the technical field of venturi scrubbers. The problems that when an existing venturi scrubber is used for a containment filtering and discharging system, the atomization effect is poor, and the filtering efficiency is affected are solved. The device comprises an inlet straight pipe section, a subsonic velocity gas contraction section, a supersonic velocity gas expansion section, a throat pipe, a subsonic velocity gas expansion section and an outlet straight pipe section which are sequentially and coaxially connected from bottom to top, the inlet straight pipe section is connected with an off-axis of an incoming flow gas nozzle to generate rotary upflow, a plurality of liquid suction holes are formed in the throat pipe, and the subsonic velocity gas expansion section is connected with the outlet straight pipe section. A plurality of exhaust holes are formed in the outlet straight pipe section, the inlet straight pipe section, the throat pipe and the outlet straight pipe section are all of straight tubular structures, and the axial included angle of the supersonic gas expansion section is smaller than that of the subsonic gas contraction section. The device is mainly used for filtering and discharging of the containment.

Description

Technical Field

[0001] The present invention belongs to the technical field of Venturi scrubbers, and particularly relates to a supersonic Venturi scrubber for a containment filtration and exhaust system. Background Art

[0002] When a severe accident occurs in a reactor, a large amount of fission products originally contained in fuel pellets and cladding are released into the containment in the form of aerosols and gases. Along with the continuous release of decay heat, the containment faces the risk of overpressure and rupture. Therefore, the containment filtration and exhaust system can be used to actively exhaust the air-steam mixture in the containment while removing radioactive aerosols and gases to ensure the integrity of the containment. The Venturi scrubber has the characteristics of simple structure and high filtration efficiency, and is widely used in wet containment filtration and exhaust systems.

[0003] Traditional Venturi scrubbers include a converging tube section, a throat section, and a diverging tube section, and are widely used in industrial processes such as desulfurization, denitrification, and dust removal. Since the air flow relies on a fan to provide power to compensate for the flow resistance, considering power consumption, the gas velocity at the throat of traditional Venturi scrubbers is less than 200 m / s. Given that the design pressure of the containment is generally higher than 0.4 MPa and the exhaust power comes from the containment-environment pressure difference, which is different from traditional industrial Venturi scrubbers. Therefore, when traditional Venturi scrubbers are used in the containment filtration and exhaust system, the atomization effect of high-pressure air flow cannot be fully utilized, reducing the filtration efficiency of aerosols and gaseous radioactive substances. Summary of the Invention

[0004] In view of this, the present invention aims to provide a supersonic Venturi scrubber for a containment filtration and exhaust system to solve the problem of poor atomization effect and influence on filtration efficiency when existing Venturi scrubbers are used in the containment filtration and exhaust system.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A supersonic Venturi scrubber for a containment filtration and exhaust system, which includes an inlet straight pipe section, a subsonic gas converging section, a supersonic gas diverging section, a throat, a subsonic gas diverging section, and an outlet straight pipe section that are coaxially connected in sequence from bottom to top. The inlet straight pipe section is eccentrically connected to an incoming gas nozzle to generate a rotating upward air flow. A plurality of liquid suction holes are provided on the throat, and the washing liquid enters the throat through the liquid suction holes. A plurality of exhaust holes are provided on the outlet straight pipe section. The inlet straight pipe section, the throat, and the outlet straight pipe section are all straight tubular structures. The cross-sectional area of the subsonic gas converging section decreases from bottom to top. The cross-sectional areas of the supersonic gas diverging section and the subsonic gas diverging section increase from bottom to top. The axial angle of the supersonic gas diverging section is less than the axial angle of the subsonic gas converging section.

[0006] Furthermore, there is an included angle between the incoming gas nozzle and the inlet straight pipe section in the axial plane, and there is an elevation angle between the incoming gas nozzle and the inlet straight pipe section in the horizontal direction.

[0007] Furthermore, the axial included angle of the subsonic gas expansion section is greater than that of the supersonic gas expansion section.

[0008] Furthermore, the aperture diameter of the exhaust hole is larger than that of the liquid suction hole.

[0009] Furthermore, the aperture diameter of the liquid suction hole is 4 - 10 mm.

[0010] Furthermore, the subsonic gas contraction section and the supersonic gas expansion section are of an integral structure.

[0011] Furthermore, the axial included angle of the subsonic gas contraction section is 18°, and the axial included angle of the supersonic gas expansion section is 10°.

[0012] Furthermore, the liquid suction hole is arranged near the supersonic gas expansion section.

[0013] Furthermore, two rows of liquid suction holes and exhaust holes are arranged.

[0014] Furthermore, the liquid suction holes and the exhaust holes are both polished.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The purpose of the present invention is to provide a supersonic Venturi scrubber for the containment filtration and discharge system, enabling it to fully exert the atomization effect of the high-pressure gas flow and improve the filtration efficiency of aerosols and gaseous radioactive substances.

[0016] The present invention adopts an off-axis gas inlet design, which can generate a spiral upward gas flow, can be fully mixed with the washing liquid, and uses the high turbulence performance of the supersonic gas to impact water droplets to form water mist, prolonging the washing time and improving the washing efficiency.

[0017] The structure of the present invention adopts a design of contraction - expansion - throat - expansion, which is different from the traditional subsonic Venturi scrubber's design of contraction - throat - expansion. This design can accelerate the subsonic gas to supersonic speed in the supersonic gas expansion section and decelerate it to subsonic speed in the subsonic gas expansion section. In this way, it not only utilizes the advantages of supersonic gas to capture aerosol particles, but also decelerates the outlet speed to subsonic speed to avoid the impact of supersonic gas on the equipment, giving full play to the advantages of supersonic gas while avoiding its disadvantages, improving the dust collection efficiency and prolonging the service life of the equipment.

[0018] The present invention provides liquid suction holes at the throat and adopts a self-priming structure. During the process of accelerating the gas to supersonic speed, the gas pressure gradually decreases, and the pressure is less than the pressure of the washing liquid. Therefore, the washing liquid enters the throat automatically, achieving self-priming. It can operate stably in a passive manner under accidents.

[0019] The design of the exhaust hole of the present invention utilizes the principle that the gas velocity decreases while the pressure increases. The increased pressure is greater than the ambient pressure. Due to the pressure difference, the gas is self-driven to leave the scrubber, while the liquid droplets remain inside the Venturi scrubber due to their greater mass and inertia, achieving gas-liquid separation.

[0020] In summary, compared with the traditional Venturi scrubber, the present invention can be more applied to the containment filtration and discharge system and has a higher dust removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0022] Figure 1 is a schematic diagram of the overall structure of a supersonic Venturi scrubber for a containment filtration and discharge system according to the present invention;

[0023] Figure 2 is a schematic diagram of the structure in which the inlet straight pipe section is eccentrically connected to the incoming gas nozzle according to the present invention.

[0024] In the figure:

[0025] 1 - incoming gas nozzle, 2 - inlet straight pipe section, 3 - subsonic gas contraction section, 4 - supersonic gas expansion section, 5 - liquid suction hole, 6 - throat, 7 - subsonic gas expansion section, 8 - outlet straight pipe section, 9 - exhaust hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will clearly and completely elaborate on the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0027] See Figure 1-2Description of this embodiment: A supersonic Venturi scrubber for a containment filtration and discharge system, which comprises an inlet straight pipe section 2, a subsonic gas contraction section 3, a supersonic gas expansion section 4, a throat section 6, a subsonic gas expansion section 7, and an outlet straight pipe section 8 that are coaxially connected in sequence from bottom to top. The inlet straight pipe section 2 is eccentrically connected to the incoming gas nozzle 1 to generate a rotating upward gas flow. A plurality of liquid suction holes 5 are provided on the throat section 6, and the washing liquid enters the throat section 6 through the liquid suction holes 5. A plurality of exhaust holes 9 are provided on the outlet straight pipe section 8. The inlet straight pipe section 2, the throat section 6, and the outlet straight pipe section 8 are all straight tubular structures. The cross-sectional area of the subsonic gas contraction section 3 decreases from bottom to top. The cross-sectional areas of the supersonic gas expansion section 4 and the subsonic gas expansion section 7 increase from bottom to top. The axial angle of the supersonic gas expansion section 4 is smaller than the axial angle of the subsonic gas contraction section 3.

[0028] In this embodiment, the inlet straight pipe section 2 is eccentrically connected to the incoming gas nozzle 1 to generate a rotating upward gas flow; the subsonic gas contraction section 3 and the supersonic gas expansion section 4 are used to ensure that the subsonic gas can be accelerated to supersonic speed; the washing liquid enters the throat section 6 through the liquid suction holes 5 in a self-suction manner; the throat section 6 has a certain length to clean aerosol particles and gaseous radioactive substances in the gas; the subsonic gas expansion section 7 is used to decelerate the subsonic gas; the exhaust holes 9 provided on the outlet straight pipe section 8 discharge the gas.

[0029] The incoming gas nozzle 1 is on the side of the inlet straight pipe section 2, and the inlet straight pipe section 2 is eccentrically connected to the incoming gas nozzle 1. There is an angle between the incoming gas nozzle 1 and the inlet straight pipe section 2 in the axial plane, and there is an elevation angle between the incoming gas nozzle 1 and the inlet straight pipe section 2 in the horizontal direction. The eccentric design can generate a high-speed rotating upward gas flow. When the generated high-speed rotating upward gas flow rotates, an asymmetric movement is generated due to the centrifugal force, which enhances the contact between the gas and the washing liquid, can better impact the washing liquid droplets, extends the washing time of the gas in the limited space, and improves the washing efficiency.

[0030] Above the inlet straight pipe section 2 is the subsonic gas contraction section 3, which is the component that accelerates the incoming gas to the speed of sound. The size of the cross-sectional area of the subsonic gas contraction section 3 determines the amount of gas flow; while the change rate of the cross-sectional area determines the magnitude of the gas acceleration.

[0031] At the upper end of the subsonic gas contraction section 3 is the supersonic gas expansion section 4, which is the key component that differentiates this invention from the traditional Venturi tube. The sonic gas is accelerated to supersonic speed under the rated working condition in the supersonic gas expansion section 4. According to the continuity equation:

[0032]

[0033]

[0034] where A is the cross-sectional area of the gas passing through the subsonic gas contraction section 3 and the supersonic gas expansion section 4 at a certain moment, and C f is the instantaneous velocity of the gas in the subsonic gas contraction section 3 and the supersonic gas expansion section 4 at this moment, v is the specific volume of the gas at this moment, Ma is the Mach number, and d represents differentiation.

[0035] It can be seen from the formula that when the Mach number is less than 1, the gas is in a subsonic flow state, and the change rate of the pipeline cross-sectional area must be negative, and the pipeline cross-sectional area gradually becomes smaller, that is, the subsonic gas contraction section 3. When the Mach number is equal to 1, the gas reaches the speed of sound. If the pipeline cross-sectional area is further reduced, the gas cannot be further accelerated. When the Mach number is greater than 1, the change rate of the pipeline cross-sectional area must be positive, which means that the pipeline cross-sectional area needs to gradually become larger, that is, the supersonic gas expansion section 4. When the Mach number is greater than 1, only in the supersonic gas expansion section 4 can the gas continue to accelerate to reach the supersonic speed required for cleaning. The geometric shapes of the subsonic gas contraction section 3 and the supersonic gas expansion section 4 determine the values of the acceleration and the supersonic speed, thus affecting the washing efficiency.

[0036] At the upper end of the supersonic gas expansion section 4 is the throat 6. The throat 6 is a component where the supersonic gas and the washing liquid are fully mixed and cleaned, so a certain length is required. Two rows of liquid suction holes are arranged near the supersonic gas expansion section 4 at the entrance of the throat 6, and the washing liquid will enter the throat 6 from here. It can be seen from the above formula that during the process of the gas being accelerated to supersonic speed, its gas pressure gradually decreases, and the pressure is less than the pressure of the washing liquid. Therefore, the washing liquid enters the throat 6 automatically, thus realizing self-priming.

[0037] Using supersonic gas for washing has the following advantages: The dust in the gas has a large kinetic energy, the dust has a large inertia, and the probability of the dust entering the liquid droplets is greater, which improves the contact probability between the pollutant and the liquid droplets; The high-speed gas has a large kinetic energy. When the gas impacts the washing liquid, it can impact the washing liquid into finer water mist. Compared with water droplets, the water mist has a larger contact area with dust, and thus captures more dust; The impact of the supersonic gas on the particulate matter is greater, reducing the deposition of particulate matter in the equipment; Compared with the washing liquid, the pressure of the supersonic gas is smaller. Due to the pressure difference, the washing liquid is sucked into the throat 6, realizing self-priming, and continuing to work in a passive manner under unpreventable disasters.

[0038] At the upper end of the throat 6 is the subsonic gas expansion section 7, and the axial angle of the subsonic gas expansion section 7 is greater than the axial angle of the supersonic gas expansion section 4. After the supersonic gas and the washing liquid are fully mixed and cleaned, the speed of the supersonic gas is reduced to subsonic speed. It can be seen from the formula that when the value becomes larger, since the gas Mach number is less than 1, The value decreases. Therefore, only when the cross-sectional area decreases monotonically can the velocity of the subsonic gas gradually decrease. As the gas pressure increases, the velocity decreases; due to its greater mass, the droplet has greater inertia and will maintain its original state of motion, facilitating gas-liquid separation.

[0039] The outlet straight pipe section 8 has two rows of exhaust holes 9, and the aperture of the exhaust holes 9 is larger than that of the liquid suction holes 5. When the gas passes through the subsonic gas expansion section 7, the gas velocity decreases and the pressure rises, and the gas pressure is greater than the external pressure. Due to the pressure difference, the washed gas leaves the Venturi scrubber through the exhaust holes 9, and the droplets are left inside, achieving gas-liquid separation.

[0040] As Figure 1 shown, the subsonic gas contraction section 3 and the supersonic gas expansion section 4 are of an integral structure. Except for the subsonic gas contraction section 3 and the supersonic gas expansion section 4, the remaining components are connected by welding to ensure the reasonable arrangement of each component in the same axial direction. The subsonic gas contraction section 3 and the supersonic gas expansion section 4 are designed with an integral structure to prevent disturbances from occurring at the connection between the two when the sonic gas is welded.

[0041] In order to ensure the stable flow of the supersonic gas in the throat 6, it is necessary to polish and buff each component, as well as the liquid suction holes 5 and the exhaust holes 9, to reduce the flow resistance and prevent accidents caused by vibrations generated by the high-speed gas flow.

[0042] The axial angle of the supersonic gas expansion section 4 is smaller than that of the subsonic gas contraction section 3. Because the velocity of the supersonic gas is too fast, in order to prevent its acceleration from being too fast and causing too much disturbance to the equipment, the angle should be smaller. The axial angle of the subsonic gas contraction section 3 is about 18°, and the axial angle of the supersonic gas expansion section 4 is about 10°.

[0043] The throat 6 can ensure the stability of the outlet supersonic gas and wash the gas. Therefore, the throat 6 needs to have a certain length, which is affected by the flow rates of both the supersonic gas and the washing liquid. The washing liquid enters the throat 6 through the liquid suction holes 5 for washing, and the washing liquid and the supersonic gas converge near the liquid suction holes 5. Factors such as gas-liquid erosion and chemical compatibility need to be considered. Therefore, the performance of the metal material here should be good, and the metal material here needs to meet the characteristics of high stiffness, corrosion resistance, and long service life. The holes are drilled using a mechanical drilling process and polished and buffed. Since the washing liquid is impacted by the supersonic gas and atomized when entering the throat 6, considering the high flow rate of the supersonic gas in the throat 6, in order to ensure that the washing liquid is fully atomized, the aperture should not be too large, and the aperture of the liquid suction holes 5 can be between 4 and 10 mm.

[0044] Since the gas has been decelerated to subsonic speed in the subsonic gas expansion section 7 after passing through the washing and impacting the washing liquid, the gas flow rate gradually decreases and the pressure gradually increases here. To ensure the increase in gas pressure, the wall surface of the subsonic gas expansion section 7 needs to be smoothed. After the gas reaches the outlet straight pipe section 8, its speed has been reduced to a very low level. Since the pressure is greater than the ambient pressure, the gas leaves the scrubber through the exhaust hole 9. The droplets, due to their greater mass and inertia, are left behind and fall back into the Venturi scrubber. A large amount of gas needs to leave the Venturi scrubber through the exhaust hole 9, so the aperture of the exhaust hole 9 is larger than that of the liquid suction hole 5.

[0045] As Figure 2 shown, the incoming gas nozzle 1 and the inlet straight pipe section 2 are connected by welding to ensure their sealing performance. To ensure the smooth generation and stability of the rotating upward gas, the inlet straight pipe section 2 needs to have a certain length. The main principle of the offset-axis design is as follows: the incoming gas nozzle 1 is on the side of the inlet straight pipe section 2, and the inlet straight pipe section 2 is connected to the incoming gas nozzle 1 in an offset-axis manner. The incoming gas nozzle 1 and the inlet straight pipe section 2 form a specific spatial angle in the axial plane, which directly affects the magnitude of the tangential velocity component of the gas and thus determines the gas rotation intensity. At the same time, there is an elevation angle between the incoming gas nozzle 1 and the inlet straight pipe section 2 in the horizontal direction, which directly affects the gas rotation angle. This elevation angle determines the magnitude of the axial velocity component of the gas and thus affects the magnitude of the gas cleaning intensity. The specific design can be determined according to the actual working conditions and washing situation.

[0046] The specific embodiments of the present invention disclosed above are only used to help illustrate the present invention. The specific embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. According to the content of this specification, many modifications and changes can be made. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well.

Claims

1. A supersonic venturi scrubber for a containment filtration and exhaust system, characterized in that: The invention comprises an inlet straight pipe section (2), a subsonic gas contraction section (3), a supersonic gas expansion section (4), a throat (6), a subsonic gas expansion section (7) and an outlet straight pipe section (8) which are coaxially connected in sequence from bottom to top. The inlet straight pipe section (2) is eccentrically connected to an incoming gas nozzle (1) to generate a rotating ascending airflow. The throat (6) is provided with a plurality of liquid suction holes (5), through which washing liquid enters the throat (6). The outlet straight pipe section (8) is provided with a plurality of exhaust holes (9). The inlet straight pipe section (2), the throat (6) and the outlet straight pipe section (8) are all straight tubular structures. The cross-sectional area of ​​the subsonic gas contraction section (3) decreases from bottom to top, while the cross-sectional areas of the supersonic gas expansion section (4) and the subsonic gas expansion section (7) increase from bottom to top. The axial angle of the supersonic gas expansion section (4) is smaller than the axial angle of the subsonic gas contraction section (3).

2. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: There is an included angle between the incoming gas nozzle (1) and the inlet straight pipe section (2) on the axial plane, and there is an elevation angle between the incoming gas nozzle (1) and the inlet straight pipe section (2) in the horizontal direction.

3. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The axial angle of the subsonic gas expansion section (7) is greater than the axial angle of the supersonic gas expansion section (4).

4. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The diameter of the air vent (9) is larger than the diameter of the liquid suction hole (5).

5. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 4, characterized in that: The diameter of the liquid suction hole (5) is 4 to 10 mm.

6. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The subsonic gas contraction section (3) and the supersonic gas expansion section (4) are an integrated structure.

7. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The axial angle of the subsonic gas contraction section (3) is 18°, and the axial angle of the supersonic gas expansion section (4) is 10°.

8. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The liquid suction hole (5) is arranged close to the supersonic gas expansion section (4).

9. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The liquid suction holes (5) and the air exhaust holes (9) are both arranged in two rows.

10. The supersonic venturi scrubber for a containment filtration and exhaust system according to claim 1, characterized in that: The liquid suction hole (5) and the exhaust hole (9) are both ground and polished.

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