SE454407B - Appts. for cleansing contaminated gas - Google Patents

Abstract

Appts. for cleaming the contaminated gas comprises a vessel partially filled with a washing or cleaning liq., an inlet for the contaminated gas and a distribution means having inlet orifices at increasing depths below the liq. level, as well as an outlet for the cleansed gas. Distributor pipes and/or distributor chamber of distribution means have openings for the gas flow facing liq. bath located udner lowermost orifice. Outlet orifices are nozzle-shaped having particle sepg. properties e.g. venturi nozzles. Vessel is divided into sections by radially extending partition walls.

Description

454 407 10 15 20 25 30 35 large and requires a considerable cost. Despite this, a relatively poor separation of the finest particles is obtained, especially particles below 0.5 .mu.m. Furthermore, such a stone bed filter has poor efficiency in the separation of gases, which here takes place by adsorption on the stone material.

Instead, according to the present invention, it is proposed to use wet cleaning by means of a liquid, where the contaminated gas is brought below the surface of the liquid. The separator will in this case function as a water trap, which when there is no overpressure in the space connected to the gas cleaner keeps it separated from the surrounding atmosphere.

In order to obtain a good cleaning efficiency in a wet cleaner, it is required that there must be an intimate mixture between liquid and gas in the cleaner. The purification liquid must thus be distributed as fine liquid bodies in the gas and / or the gas must be caused to pass through the liquid in the form of small gas bubbles. For wet cleaners, where the gas is introduced below the liquid surface, it also applies that the purification efficiency is very flow-dependent, and good purification is only obtained within a relatively narrow flow interval.

This presents particular problems in the present case, since an emergency system must be able to cope with variably large flows without any active control or regulation.

It has previously been proposed a purification device according to DE-PS 228 733 where incoming gas flows are divided into a number of sub-flows and are caused to strike impinging or abutment surfaces like fine jets. However, this device has the above-mentioned limitation that it has low efficiency at low gas flows, since the gas will then bubble through the liquid relatively unaffected in the form of large air bubbles.

Wet cleaning devices have also been proposed according to US-A 3,216,181 (see Fig. 4), U5 ~ A 3,520,113 (see Fig. 7) and US-A 4,182,617 (see Fig. 2), in which the gas is introduced under the surface of the liquid through a number of openings at gradually increasing depths.

In use, the incoming gas presses with increasing gas flow and inlet pressure down the liquid surface in the inlet line until the first outlet opening is exposed and the gas is caused to flow up through the liquid. With increasing flow and inlet pressure, the liquid surface is pressed down further and more and more openings are exposed, so that the gas can flow out through these as partial flows. In this way, at least substantially the same flow can pass through the used outlet openings independently of the inlet pressure and the total flow through the gas purification device.

These prior art gas purification devices have the disadvantage that when the liquid surface in the inlet solution is pressed down under an inlet opening, the gas will be forced out into the purification bath with low energy and without any pressure drop. The gas will therefore flow out into and up through the liquid as relatively large bubbles and there is therefore a poor separation of fine particles and gaseous pollutants. Such a previously known retrieval device is thus not sufficiently a passive emergency system for separating highly toxic particles, for example in the event of a nuclear accident. The object of the present invention is therefore to remedy the shortcomings of the prior art and to provide a process for purifying gases of the above-mentioned kind, which has a high degree of separation for particulate pollutants even for the finest particles, which can be separated even gaseous pollutants and which can work without power supply from outside.

The degree of separation of contaminants should be largely independent of the gas flow. A further object of the invention is to provide a device for carrying out the process, which has a simple construction, low manufacturing costs and which operates without active mechanical components and active efforts of operating personnel. Furthermore, the device must be possible to clean up with rational methods after an operation.

In order to achieve this, the method according to the invention is characterized above all by the features stated in the characterized part of claim 1. The device according to the invention is characterized above all by the special features specified in the characterized part of the first device requirement. 454 WJI 10 15 20 25 30 35 40 407 4 In the process or device according to the invention, a high purification efficiency is always obtained regardless of the size of the total gas flow. By causing the polluted gas to pass through first inlet openings at a gradually increasing depth below the liquid surface and then through outlet openings at a higher height than the corresponding inlet opening, it is guaranteed that the polluted gas always passes the outlet nozzle with a considerable pressure drop between the inlet opening and the outlet opening. In this way, the gas which passes through the last used outlet openings will also undergo a considerable pressure drop and thus obtain a complete purification.

Because the distributor opens freely downwards towards the liquid bath, the cleaning liquid can rise in the distributor in the event of decreasing inlet pressure (= cessation of operational disturbance), so that the liquid rises again over some or all of the previously free inlet openings and blocks the gas flow through them without disturbance.

According to a particularly advantageous embodiment, its outlet nozzles consist of venturi nozzles, which in their walls have inlet openings towards the surrounding liquid bath. In this way, no special supply is required for cleaning fluid and a constant and safe fluid supply to the venturi nozzles is guaranteed.

By means of the invention a high degree of separation of particles and liquid droplets by absorption can be achieved within a wide range of sizes. Gaseous contaminants are separated by dissolving them in the washing liquid and / or reacting with substances involved in the washing liquid.

According to the invention, the pressure of the gas in an enclosure after a malfunction is advantageously utilized to drive it through the gas purification device. In this way, you can work completely independently of external power sources.

The purification device according to the invention can also be used as a separator in the process industry. It can then be combined with a pre-connected fan or the like, if the polluted gas does not have sufficient overpressure. The same applies if the purification device according to the invention is to be used in disturbance situations, where there is no or no overpressure occurs. According to the invention, the number of substreams is automatically adapted to the total flow, so that each substream represents the same or substantially the same flow independently of the total flow.

In the case of partial loads, the outlet openings can be made to be connected successively by arranging the outlet openings or the gas inlets to their manifolds at gradually increasing depths.

In order to withstand the occurring pressures, the outer wall of the gas purification device is suitably designed as a pressure vessel.

Controlling partitions advantageously ensure that a backflow channel is formed from the area at the liquid surface to below the outlet openings for polluted gas. The rising gas bubbles give a mammoth pumping effect and create a liquid circulation. In this way, a local depletion or consumption of smoke additives in the washing liquid is counteracted and a cooling is obtained, in that the liquid at the bottom also communicates with non-activated parts of the separator.

The invention will now be described in more detail in the following detailed description of exemplary embodiments with reference to the accompanying drawing.

In the drawing: in Fig. 1 a vertical section of a first embodiment of a gas purification device according to the invention, 2 a horizontal section along the line II-II in Fig. 1, 3 shows a detail of Fig. 1 showing an outlet opening with an opposite impingement. or abutment means, "4 a vertical section of a second embodiment of a gas purification device according to the invention," S a horizontal section along the line VV in Fig. 0, 6 a detail view showing a partition wall provided with inclined lamella settling plates for separating gas bubbles and particles from recirculating washing liquid .

Figures 1-3 show in a roughly schematic form a gas purification device comprising a pressure vessel 1 with outer wall 10, bottom 11 and lid 13; an inlet 12, a distributor 14 and an outlet 16. The distributor consists of a number, in example six, of radial, obliquely downwardly directed distributor tubes 18. The manifolds have an outer, vertical, downwardly directed pipe section 20 with a downwardly directed, free opening ÉZ. On their oblique parts, the manifolds 18 have risers 24 connected to transverse distribution pipes 26 via gas inlets or inlet openings 64. As best seen in Fig. 3, the distribution pipes 26 have outlet nozzles 28 for polluted gas with outlet openings or orifices 31. Outlets , of which only 10 are shown in Figures 1 and 2, may advantageously be in the form of venturi nozzles, which preferably have suction openings 29 for washing or cleaning liquid towards the surrounding liquid bath 32. Above the outlet nozzles are arranged spreading means in the form of impingers. or abutment surfaces in the form of angle iron 30 on a support structure (not shown).

The manifold 14 is immersed in a liquid bath 32 at a certain depth below its surface 34 and has an inner liquid surface 46, 20 whose position depends on the pressure of the incoming gas. In use, the gas will flow out with a pressure drop corresponding to the height difference h between the respective outlet opening 31 and the inner liquid surface 46. Between the gas cleaner liquid surface 34 and the outlet 16 there is arranged a substantially horizontal intermediate bottom 36. The intermediate bottom 36 has a number of passage openings 38. with only schematically shown separating devices 40 for fine liquid droplets and any particles. These separating devices can in principle be of any kind. Cyclone devices, however, have proved to be particularly suitable. Separated liquid can then, as shown in Fig. 4, be brought down below the liquid surface 34 via an extension tube 42. The extension tube 42 can then be protected, for example by means of a hood 35 (not shown), against direct penetration of gas bubbles. In the space 44 above the partition wall 36, in a manner known per se, additional separating means for particles and liquid droplets can be arranged in front of the outlet 16. The outlet 16 can in turn be connected to a further purification device or lead directly to a chimney or other discharge means.

The function of the gas purification device is as follows. In the unloaded state, washing liquid penetrates through the openings 29, 31 and the lower openings 22 of the outlet nozzles 28, so that an inner liquid surface 46 in the distributor 1a and the inlet pipe 12 assume the same position as the outer liquid surface 3A. The gas purifier now has a water trap function. In the event of a malfunction with gas emissions, the pressure is increased and the inner liquid surface 46 is pressed down, until it falls below the threshold at the highest inlet openings 64 to the outlet nozzles 28.

The gas then penetrates through these outlet nozzles, whereby it sucks in finely divided liquid droplets during the passage past the intake openings 29. Solid and liquid impurities as well as polluting gases are absorbed by the suction liquid droplets. The effluent gas strikes the impinger or abutment surfaces 30, and decomposes into fine gas bubbles, which rise through the washing liquid 32. The gas is further purified here by a washing bottle effect, whereby the now pollutant liquid droplets, dust particles and gaseous contaminants are taken up by washing liquids.

The separation of pollutants thus takes place in two steps. In a first step, dust separation and absorption of gases and ions by venturi and / or impinging effect takes place by inertial forces in and at the outlet nozzles 28 and the impinger or abutment surfaces 30. In a second step, dust separation and absorption of gases takes place by a wash bottle effect , ie absorption, sedimentation and / or diffusion during the path of the gas bubbles through the washing liquid up to the liquid surface 34.

Separation of gases in the contaminated gas can be facilitated by mixing suitable substances in the washing liquid, which substances react with the contaminants. For example, for the absorption of gaseous iodine, the washing liquid can be mixed with sodium thiosulphate.

Stagnant washing liquid in the upper part of the liquid mass 32 risks becoming saturated with impurities or depleted of active additives. In order to counteract this and achieve a liquid circulation, in the first embodiment a guiding partition wall 48 can be arranged next to the outer wall 10 in a corresponding manner as in Fig. 4. The liquid-filled inner space will thereby function as a mammoth pump, whereby substantially bubble free washing liquid circulates down through a slit-shaped space 50 between the guiding partition wall 48 and the outer wall 10.

This partition wall 48 should then extend below the level of all outlet nozzles 28 to ensure a good liquid circulation.

The embodiment shown in Figures 4 and 5 comprises a modified distributor 14 'with a centrally located, cylindrical distribution chamber 52 and from there at different levels emanating, obliquely upwardly directed distribution pipes 54. The distribution pipes 54 are continued by radially downwardly directed parts 56 with horizontally projecting distribution pipes 58. These distribution pipes 58 have non-drawn and only shown in an enlarged detail view outlet nozzles 28 and may be provided with impinging or abutment surfaces 30 located above, as shown in Figures 1-3.

The gas cleaning device according to Figures 4 and 5 is divided into sections by means of radial partitions 60, which are bounded upwards by the partition bottom 36 and downwards extend below the level of the outlet nozzles 28. Inwards they connect to the inlet pipe 12 and outwards to the outer wall 10. arranged a circumferential, guide partition wall 48, which at the top extends over the liquid surface 34 under rest conditions and downwards to near the bottom of the device 11. The partitions 60 can extend down into the slit-shaped space 50 and serve as bracing for the guide partition wall 48. This however, is not required for the operation of the cleaning device, and instead the partition wall 48 may be attached by struts to the outer wall 10.

The distribution pipes 54 have gas inlets 64 in the wall of the distribution chamber 52 at different height levels. In this way, a step-by-step connection of the various cleaning sections with increasing inlet pressure is made possible. When a rocker inlet 64 is released, by pressing the inner liquid surface 46 down to a lower level, the contaminated gas can flow up through the manifold 54, 56 and out through the distribution pipes 58 and their outlet nozzles 28.

Due to the height difference h between the liquid surface 46 and the distribution pipes 58, there will be an overpressure corresponding to the height difference in the outlet nozzles 28. As a result, the polluted gas can flow out with a strong pressure drop through the outlet nozzles 28, which guarantees a good purification effect and fine decomposition. small bubbles. As an example, 99% purification efficiency can be obtained in a venturi nozzle at a pressure drop of 104 Pa, corresponding to 1 m of water column. Because the gas inlets 64 are raised, it becomes possible in this way to connect section after section with full arranged on different at partial load automatic cleaning effect. This is of particular importance for efficient dust separation.

The effects of inertia are strongly dependent on the gas velocity and a low velocity gives poor separation.

Due to the density-reducing effect of the gas bubbles, the working gas purification sections 66 will have a higher liquid level 34 '. This liquid surface '34 'lies above the upper edge 68 of the guiding partition wall 48. In this way a recirculation of washing liquid from the very sections 66 which work and are supplied with contaminated gas is made possible. Especially in the case of partial loads, this prevents a local enrichment of contaminants or depletion of additives in the upper parts of the working sections.

Fig. 6 shows a detail view of the slit-shaped space 50, in which inclined lamella sedimentation plates 74 are arranged. These plates 74 delimit a number of inclined spaces 72, which are limited at the top and bottom by said lamella sedimentation plates 74. gas bubbles 76 will rise towards the upper limited plate I an amount of liquid introduced into such an inclined space, and particulate material, to sink against the lower limiting plate. The gas bubbles 76 then rise along the underside of the above-mentioned plate up to the liquid surface 34 and 34 ', respectively. The sediment-bearing particles 78 slide down along the surface of the underlying plate and finally fall down towards the bottom 11 of the vessel from the lower edge 80 of the respective plate.

The use of lamella sedimentation plates results in a lateral movement of recycled liquid. In this way, during partial loading, the liquid is recirculated to the same cell and thus depletion of the additives is prevented.

For cooling or, exceptionally, heating of the liquid in the gas purification device, a heat exchanger coil (not shown) can be arranged in the vessel.

The vessel should have a sufficiently large volume to be able to hold condensate and separated solid particles during use in the event of a malfunction. During process cleaning, condensate and separated solid particles can be taken out through the normally closed bottom outlet 8 of the container, for example through a lock arrangement with two valves in a row.

The impinger or abutment surfaces can have any design.

For example, they may consist of a perforated plate arranged above the outlet openings 31. Such a plate also has a distributor effect, so that formed gas bubbles are distributed over the entire surface and available volume is better utilized.

The vessel l can for some applications be freely open upwards.

The side walls 10 must then go high enough to prevent splashes. Such a vessel can then be equipped with further separating devices, such as for instance grids or filters For separating liquid droplets and / or stationary or fluidized particle beds above or below the liquid surface.

The guiding partitions 48 can be arranged at arbitrary places in the vessel 1 to separate gap-shaped spaces 50, for example next to the radial partitions 60 or in pairs with connecting short walls. Conveniently but not necessarily, they are placed between different sections 66 or between parts served by different manifolds 18, 54. The vessel 1 need not be circular but may have any shape depending on, for example, local circumstances, e.g. rektenguiärc ene: eregeibundet. furthermore, the inner tube 12 'can be connected to the vessel in any place, for example asymmetrically in the lid 13, or even through the side wall 10 of the vessel or its bottom 11. The main thing is that the inlet connects to the distributor 14 and 14 ', respectively, above the highest gas inlet 64.

The outlet openings 28 can be connected in any way with the respective associated gas inlet in the distributor 14, 14 '. In most cases, a device comprising horizontal or self-drainage reasons slightly inclined distribution pipe 26, 58 and manifold 18, 54, 56 is the most suitable solution. The riser 24 can be made considerably higher than in the example, so that a considerable height difference h arises, and thus a high outflow pressure, as soon as the gas intake of the riser at the bottom comes above the inner liquid surface 46.

A gas purification device according to the invention can be made arbitrarily large, and comprises several spacers 14 and / or 14 'separated from each other and independent of each other. Furthermore, a gas purification plant can consist of several separate gas purification devices placed in groups or at a distance from each other. The latter facilitates maintenance work, such as pipe work, and enables the shutdown of individual units while maintaining preparedness.

The gas purification device according to the invention can thus be given very large dimensions. For an emergency system at a nuclear power plant, the area can, for example, amount to 50-100 m2 and the diameter of the device can be 10 m or larger. The starting volume of liquid must also be large enough to provide a margin for liquid losses. In the event of a discharge in the order of 10 kg / sec at a temperature of 150 ° C, there is a risk of boiling water in the order of 1.0-3.5 m3 / h. Additional fluid losses occur in the form of mist drops. The invention is not limited to the embodiments shown but can be varied in any manner within the scope of the following claims. In particular, it is possible to arbitrarily combine the various partial solutions shown in the drawing examples and / or mentioned in the description in an arbitrary manner in constructions of a gas purification device according to the invention. v

Claims (10)

10 15 20 25 30 35 ß 454 407 PATENTKRAV A method of purifying a gas from solid, liquid and / or gaseous contaminants by bubbling the gas through a liquid bath (32), and passing the incoming gas into a manifold (14, 14 ') and passing it. as partial flows through a number of inlet openings (64) at successively increasing depths below the surface (34, 34 ') of the liquid (32), the gas flow at increasing inlet pressure being passed through an increasing number of inlet openings (64) at the corresponding inlet pressure increasing depth (below liquid level) 34, 34 '), so that with increasing inlet pressure increasing number of inlet openings (64) is used for an increasing number of substreams, so that at least substantially the same flow passes through the used inlet openings independent of the inlet pressure and the total flow through the gas purification means, This means that the gas flow from the respective inlet opening (64) is caused to pass through connecting means (24, 26, 28; 54, 56, 28) to the outlet opening. (31) at a higher height (h) than the corresponding inlet opening (64) and is caused to pass out into the liquid bath (32) with a pressure drop corresponding to the height difference (h) between the respective outlet opening (31) and an inner liquid surface (46) in said distributor (14, 14 '). 2. A method according to claim 1, characterized in that the gas flow during its passage through said connecting means is restricted, so that high velocity gradients occur, 28), wherein. preferably washing liquid is sucked in through openings (29) arranged in the venturi, for example in venturi nozzles (outlet nozzles of the walls of the nozzles) towards the surrounding liquid bath (32). 3. A method according to claim 1 or 2, characterized in that the gas sub-currents upon their entry into the liquid bath (32) are caused to strike means (impinger or abutment surfaces 30) which split the respective gas jet into fine bubbles, which may pass up through the liquid while releasing contaminants into the liquid. 10 15 20 25 30 454 407 | Q Device for carrying out the method according to claim 1, 2 or 3, comprising a vessel (1) partially filled with a washing or cleaning liquid (32), an inlet (12) for contaminated gas, a distributor (14, 14). ') which has a plurality of inlet openings (64) for the incoming polluted gas at a gradually increasing depth below the surface of the liquid' (34,} 4 '), and an outlet (16) for purified gas, wherein at increasing inlet pressure the liquid surface or the liquid surfaces (46) in the interior of the Manifold (14, 14 ') is pressed down, so that inlet openings (64) are exposed at successively increasing depths and allow gas outflow through them, characterized in that connection means (64) emanate from the respective inlet opening (64). 24, 26, 28; 54, 56, 58, 28) to outlet openings (31) for sub-streams of contaminated are given at a higher height Od than the corresponding inlet opening (64) and below the liquid surface (34, 34 '). Device according to claim 4, characterized in that a distributor chamber (52) and / or distributor tubes (18) included in the distributor (14, 14 ') have openings (22) towards the liquid bath (32) located below the bottom for gas outflow intended inlet opening (64). Device according to claim 4 or S, characterized in that a large number of outlet openings (31) are arranged below preferably substantially the entire surface of the liquid ('54, inheritance), and / or now the height difference (h) between the outlet openings (31) and the respective corresponding inlet opening (64) is approximately 1 m. Device according to Claim 4, 5 or 6, characterized in that the outlet openings are designed as nozzles with particle-separating properties, for example venturi nozzles (outlet nozzles 28) which preferably have openings (29) in the wall towards the surrounding liquid bath (32). d; 10 15 20 25 30 35 454 407 I5 Device according to at least one of Claims 4 to 7, characterized in that the vessel (1) is divided into sections of radial partitions (60), which extend from an area below the outlet openings (31). up over the surface (34) of the gas-laden liquid and preferably up to an intermediate intermediate bottom (36). Device according to one of Claims 4 to 8, characterized in that one or more guide partitions (48) are arranged, for example next to the outer wall (10) of the vessel (1), the radial partitions (60). or in pairs opposite and delimiting one or more preferably slit-shaped spaces (50), through which liquid lifted by flowing gas can be recirculated down to the lower part of the vessel (1), said one or more guide partitions (48) preferably extends up over the surface (34) of the liquid under resting conditions but not up to the surface (34 ') of the gas-laden liquid, and / or wherein the lower edge of the guiding partition (48) is preferably located below the inlet openings (28), and / or wherein inclined lamella sedimentation plates (74) are arranged in at least some of said one or more slit-shaped spaces (50). Device according to at least one of Claims 4 to 9, characterized in that separating devices for liquid droplets and any remaining contaminants are arranged above the liquid surface (34, 34 '), the vessel preferably being a closed vessel (1). ) and comprises a lid (13) with at least one outlet (16), an intermediate bottom (36) being arranged above the highest liquid slide (34 ') and separating a space (44) in front of said outlet (16), and with said intermediate bottom (36) having openings (38) separating devices (40), for example cyclones, intended for separating fine liquid droplets and particles, which undercaps of cyclones are preferably led down through an extension tube (42) below the liquid surface (34).