INSTALLATION FOR CLEANING GASES, ESPECIALLY FIRE SMOKE GASES

Abstract: A scrubber installation (1) for cleaning, for instance, fire smoke gas comprises a preseparator (13) having at least one perforated plate (19, 19') upstream of which a set of first nozzles is arranged, with the purpose of spraying the upstream side of the plate with flushing liquid so as to dampen and cool the smoke gas and flush the holes of the plate. One or more sets of nozzles (25, 25') are arranged downstream of the plate which squirt liquid in the reverse flow of the gas through the holes with the purpose of dampening and cooling the gas additionally. Water steam is condensing on the solid particles acting as condensation nuclei, which still are included in the gas when it passes the plate, the liquid and the particles forming agglomerates the sizes of which facilitate separation in the following cleaning devices (14, 15, 16).

Description: INSTALLATION FOR CLEANING GASES, ESPECIALLY FIRE SMOKE GASES Technical Field of the Invention This invention relates to an installation for cleaning gases, especially fire smoke gases, comprising a scrubber or wet separator through which the gas may pass from an inlet towards an outlet and in which several cleaning devices are included following each other in the direction of the gas flow. Background of the Invention Emissions of gases in the form of smoke gases cause environmental problems not only in the cases when the emissions take place more or less continuously as a result of, e.g., industrial activity, but also in the case when the emissions are of a temporary and relatively transitory character, such as when fires arise unintentionally. Emission of smoke gas is particularly annoying in connection with fires in subterranean premises or spaces. The ordinary ventilation systems at subterranean installations such as garages, tunnels, department stores, warehouse premises and the like, often mouth at the ground- level and if the fire smoke is to be evacuated through this system, the warm, dirty and not seldom poisonous smoke is emitted in the immediate adjacency to people and other living creatures. Therefore, such emissions are injurious to the health and at times directly life-threatening. To use scrubber installations for the general purpose of cleaning gases is known for a long time back. Thus, scrubbers are used for cleaning welding smoke, gases from acid baths, smoke gases from industrial combustion processes, etc. These previously known scrubbers are usually based on the use of a circulating liquid flow, the gas being brought to pass one or more cleaning devices which include layers of filling bodies or filter elements so as to give the best possible efficient adsorption of gas. However, this technique is not very effi- cient in practice, among other things because of the fact that the filling bodies are warmed up by the gas and thereby gives a mediocre adsorption. Another disadvantage is that the filling body layers are quickly clogged in case the gas contains a certain quantity of solid constituents. This is always the case with fire smoke gas which contains considerable amounts of soot, flakes and other solid constituents of a marked size. Qfrj-art.g and Features of the Invention The present invention aims at obviating the abovementioned shortcomings of previously known scrubber installations and at creating an improved installation. Thus, a primary object of the invention is to create a scrubber installation particularly suitable for cleaning fire gases, which installa- tion should not only give an efficient cleaning of fire smoke in respect of solid as well as gaseous constituents, but which should also be capable of working in an optimal way even when it is being flowed through by extremely large quantities of fire smoke. In other words, the installation should be able to work during a period of at least several hours without being clogged by larger solid constituents of the kind which normally constitutes a large share of fire smoke. A further object is to create an installation from which separated, solid as well as gaseous constituents may be evacuated in a simple way. It is also an object to create a scrubber installation which efficiently lowers the temperature of the smoke gases flowing through to a minimum level before they are let out in the open air. According to the invention, at least the primary object is attained by the features defined in the characterizing clause of claim 1. Preferred embodiments of the scrubber installation according to the invention are furthermore defined in the dependent claims . Brief Description of the Appended Drawings In the drawings : Fig 1 is a schematic illustration of a first embodiment of the installation according to the invention, Fig 2 is an enlarged detail section showing a preseparator , characteristic for the invention, included in the scrub- ber, Fig 3 is a schematic planar view from above showing an alternative scrubber according to the invention, and Fig 4 is a very enlarged detailed view illustrating separation elements included in a secondary cleaning device of the scrubber. Detailed Description of Preferred Embodiments of the Tπvpnfinn In fig 1, reference numeral 1 generally designates a scrubber which in the given example is intended to be located subterraneanly so as to, when necessary, serve a likewisely subterraneanly located, arbitrary installation, e.g. a road or railway tunnel, a salesroom, a garage or the like. The ground level is schematically indicated at 2. At said ground level, a house 3 is shown through which cleaned gas may be let out into the open air. The scrubber 1 is connected with the house 3 via an outlet 4 in the form of a wide sleeve coupling or pipe. An inlet 5 of the scrubber is connected with a wide tube 6 which delimits an inlet channel for untreated fire smoke. In said inlet channel 6, at least one fan 7 works by means of which the fire smoke may, from individual suction spots, be evacuated from the spaces in which a fire has arisen. One or more sprink- ler devices 8 , 8 ' may also be arranged in the inlet channel so as to initially dampen and cool the arriving fire smoke, the temperature of which often may come up to the magnitude of 400°C. The scrubber 1 is delimited by a box-shaped house com- prising side walls 9, a roof part 10 and a bottom 11 in which a collection tray 11' is included. In said tray, water or liquid may be collected and led away via a draining pipe 12. When the incoming fire smoke passes through the scrubber from the inlet 5 towards the outlet 4, it passes a number of cleaning devices following each other in the direction of the gas flow, a first device being generally designated 13. Three secondary cleaning devices are designated 14, 15 and 16. Characteristic of the first or primary cleaning device 13, which serves as a preseparator in the scrubber, is that said device includes at least one perforated plate upstream which at least one set of first nozzles 17 is arranged, the purpose of which is to spray the upstream side of the plate with flushing liquid, in particular water (possibly with special additives) . In the embodiment shown in fig 1, the perfo- rated partition wall is composed of two plates 19, 19', which are located at an obtuse angle to each other. Thus, said two plates 19, 19' form a roof-like, V-shaped construction which, together with the side walls 9 and the bottom 11, delimit a lower chamber 20 of the scrubber. In practice, it is preferred to manufacture the plates 19, 19' of a perforated steel plate having a relatively large thickness (see also fig 2) , although also other materials are feasible. In case steel plate is used, it may be of a thickness of 3 - 6 mm, the diameter of the indi- vidual holes 21 attaining 8 - 12, suitably 10 mm. The total hole area for all holes 21 should be within the range of 25 - 35%, suitably approx. 30% of the area of the plates. The individual holes may be of a substantially cylindric shape (bevels may be provided at one of the ends or both) and extend perpen- dicularly to the plane of the plate. At a certain distance in front of or upstream the plates 19, 19', a number of pipes 22 extend, each one of which is equipped with a plurality of nozzles 17. Said nozzles are mounted in such a way and are of such a nature that they squirt water in one or more jets 24 which are oblique in relation to the plane of the individual, perforated plate. For this purpose, so called flat nozzles are advantageously used, which, by the fact that they have thin, elongated mouths, bring the water to be spouted in flat jets. When the water is spouted with a high pressure, the individual jet will therefore get a knifelike character. An important purpose of the water being spouted with high pressure from said first nozzles 17 is to dampen and cool the arriving fire smoke at the same time as it separates solid constituents, such as soot flakes, from the smoke. Not least important is also the task of flushing the holes 21 of the plates. In this connection, it should also be mentioned that the cross-section-wisely V-shaped construction which is brought about by the obliquity of the perforated plates 19, 19', guar- antees an even pressure distribution of the fire smoke coming into the chamber 20, more precisely in such a way that the pressure will be approximately uniform over all holes. At a certain distance downstream the perforated plates, more precisely in a space designated 20', two sets of second nozzles 25, 25' are arranged which squirt water in the reverse flow of the gas passed through the perforation holes. The water which is spouted from said nozzles dampens and cools the smoke or the gas additionally. The nozzles are applied to pipes 26. Said pipes are connected with a water-conduit system in its entirety designated 27 which, via an inlet pipe 28, receives fresh, relatively cold water from a suitable external source. Pumps 29 and valves 30 to distribute the water in an appropriate way, not only to the scrubber, but also to the sprinkler devices 8, 8' located upstream thereto, are included in the water-conduit system. The transverse pipes 22 which carry the first nozzles 17 are also, via collecting pipes 26' , connected with the water-conduit system 27. The secondary cleaning device designated 14 may advanta- geously consist of a set of curved traps-equipped separation plates of the kind which are commercially available under the trade mark LECHLER-plate . An example of the design of such separation plates is shown in fig 4. As may be seen in this figure, the mixture of gas, water and/or water steam is led in curved paths between adjacent plates 31, said mixture, during its flow, meeting horseshoe curve-like plate portions 32, 32' forming traps into which water drops and other solid particles are collected so as to run down either in the reverse flow of the smoke feeding direction (in the embodiment according to fig 1) or in the direction perpendicularly to the feeding direction of the smoke gas (in the embodiment according to fig 3) . In the embodiment according to fig 3, the scrubber 1' is located lying or horizontally between an inlet 5' and an outlet 4'. In the same way as in the previously described embodiment, the scrubber 1' includes a preseparator 13'. In this presepara- tor, one single, substantially vertical, perforated plate or sheet 19" is included. First nozzles 17' are arranged upstream of said perforated sheet. Second nozzles 25" in one or more sets are arranged downstream of said sheet. Thus, the only sub- stantial difference between the embodiment according to fig 1 and 3, is that the last -mentioned one uses one single, plane hole plate 19" . In both of the embodiments, the secondary cleaning devices 15, 16 may consist of threads or net arranged in lat- tice and/or grid form on which water drops and solid particles may get deposited. In practice, such net constructions which are commercially available under the trade mark KIMRE may advantageously be used. The Function and Advantages of the Installation According to the Invention When the arriving fire smoke is fed into the chamber 20 by the fan 7 at a certain velocity and pressure and meets the perforated plate or plates, a pressure and velocity escalation takes place when the smoke passes the individual holes . At the same time, a turbulent stream is obtained which to a high extent increases the contact area between the passing smoke gas and the water which is squirted into the gas stream by the first nozzles 17 and mixed with the smoke gas. Since the nozzles are directed in such a way that the flat, knife-like jets are oblique against the plane of the perforated plate, an efficient flushing of the holes is obtained, guaranteeing that soot flakes and similar relatively large constituents do not get stuck in the holes . The oblique inclination of the water jets also contributes to an increase of the turbulent motions of the smoke gas passing through the holes. The water which the nozzles 17 spout towards the upstream side of the perforated plate forms, in practice, a barrier through which all smoke gas has to pass before it penetrates the holes. By using a relatively high pressure in the water which is spouted via the nozzles, the water drops are broken into very fine droplets when they hit the plate and the holes therein. By the turbulent stream which arises in the holes, an additional decomposition of said fine droplets takes place, the actively gas-adsorbing contact surface of the drops being enlarged in an advantageous way. When the smoke gas has passed through the perforated holes 21, it expands and during this expansion, the temperature of the by now supersaturated gas falls. This fall is further amplified by the fact that additional, fresh and cold water is squirted into the space 20' downstream of the perforated plate by the second nozzles 25, 25'. Thus, said water is considerably colder than the smoke gas which is fed into the space 20' bet- ween the perforated plate and the secondary cleaning device 14. The solid, relatively small particles which have not been separated from the smoke gas stream will now form condensation nuclei for the water steam which occurs in the space 20', said water steam condensing and growing together with the particles to larger agglomerates. Said larger agglomerates are relatively simple to separate in the following cleaning devices 14, 15, 16. By the fact that large amounts of cold water are squirted in with a high pressure while generating extremely small water drops, a strong cooling effect is obtained. This cooling effect is further amplified by the fact that the water steam which is formed by heating water is condensed during agglomeration. The fact that small drops are formed also means a strong increase of the solubility of the gas phases in water. Since water is not circulated in the scrubber, but rather added continuously to the piping system in a fresh, cold state, the water may always solve maximum amounts of gas. By calculating required amounts of water considering desired cooling and condensing effect, as well as the need of the water being able to solve the gas phases included in the fire smoke without the water having the time to become saturated before leaving the scrubber, a maximum and very high separation degree is obtained for the solid as well as the gaseous phases in the smoke. The water drops which are formed by condensation of water steam on solid particles and the water drops which in other respects follow with the smoke gas stream through the scrubber, finally arrive to the finishing cleaning devices 14, 15, 16. In the first one of these, viz . the device 14, which functions as a dewatering device, the gas roughly cleaned in the preseparator will be submitted to dynamic direction alterations during which water drops being heavier than the gas molecules are separated and drained through the scrubber and the draining pipe thereof . The drops which are not separated in the cleaning device 14 will pass to the devices 15, 16 in which not only screen effect and dynamic direction alteration but also surface tension are used to further enlarge the water drops and/or the particles so that these are separated when they have grown to a size which no longer admits passage through the close-meshed grid which is included in the devices. Thus, when the gas is let out in the open air after having passed the scrubber in its entirety, it is not only cooled but also efficiently liberated from the major part of the solid and gaseous constituents which initially accompanied the fire smoke . Feasible Modifications of the Invention The invention is not solely restricted to the embodiments described and shown in the drawings. Thus, it is conceiv- able to apply the invention also when cleaning other gases than hot and heavily soiled fire smoke.

Claims: Claims 1. Installation for cleaning gases, especially fire smoke gases, comprising a scrubber (1) through which the gas may pass from an inlet (5) towards an outlet (4) and in which several cleaning devices (13, 14, 15, 16) are included following each other in the direction of the gas flow, c h a r a c t er i z e d in that a first cleaning device (13) serving as a preseparator includes a perforated plate (19, 19', 19") upstream of which at least one set of first nozzles (17) is arranged, the purpose of which is to spray the upstream side of the plate with flushing liquid, in particular water, with the purpose of dampening and cooling the gas, as well as flushing the holes (21) of the plate at the same time as it separates larger constituents from the gas, and that one or more sets of second nozzles (25, 25') are arranged downstream of the plate with the purpose of squirting liquid in the reverse flow of the gas passed through the perforation holes with the purpose of dampening and cooling the gas additionally as well as bringing water steam to condense on the solid particles which still are included in the gas acting as condensation nuclei, the liquid and the particles forming agglomerates the sizes of which facilitate separation in the following cleaning devices (14, 15, 16) . 2. Installation according to claim 1, c h a r a c t e r i z e d in that the total cross-section area of the perforated holes (21) amounts to 25 - 35%, suitably approx. 30% of the area of the plate (19) . 3. Installation according to claim l or 2, c h a r a c t er i z e d in that the individual first nozzle (17) is arranged to squirt liquid in one or more jets (24) which are oblique relative to the plane of the perforated plate. 4. Installation according to claim 3, c h a r a c t e r i z e d in that the nozzle (17) consists of a flat nozzle which spouts the liquid in a flat jet. 5. Installation according to any one of the preceding claims, c h a r a c t e r i z e d in that a plurality of first nozzles (1) is mounted on a common pipe (22) located at a certain distance upstream of the perforated plate.

Inventors: AFANASJEV ALEXANDR V, DAVYDKIN NIKOLAY F, LARSSON BERTIL, MALININ NIKOLAY N, OESTRAND LARS, AFANASJEV, ALEXANDR V., DAVYDKIN, NIKOLAY F., LARSSON, BERTIL, MALININ, NIKOLAY N., OESTRAND, LARS
Applicants: AFANASJEV ALEXANDR V, DAVYDKIN NIKOLAY F, LARSSON BERTIL, MALININ NIKOLAY N, OESTRAND LARS, SAFE ROAD AB, AFANASJEV, ALEXANDR V., DAVYDKIN, NIKOLAY F., LARSSON, BERTIL, MALININ, NIKOLAY N., OESTRAND, LARS
Application year: 1997
Main classification: B01D47
IPC codes: B01D47