WO2008073022A1

WO2008073022A1 - Scrubber device for gas cleaning

Info

Publication number: WO2008073022A1
Application number: PCT/SE2007/001100
Authority: WO
Inventors: Lars ÖSTRAND; Bertil Larsson
Original assignee: ARESPÅNG, Berton; Wallin, Thomas
Priority date: 2006-12-15
Filing date: 2007-12-12
Publication date: 2008-06-19
Also published as: SE0602708L; SE530684C2

Abstract

Installation for cleaning gases, especially fire smoke gases and/or exhaust gas from vehicles, comprising a scrubber (1''') through which the gas may pass from an inlet (5''') towards an outlet (4''') and in which a first, second, third and fourth cleaning device (13''', 14''', 15''', 16''') is included following each other in the direction of the gas flow, of which a first cleaning device (13''') serving as a preseparator includes a perforated plate (19''') upstream of which at least one set of first nozzles (17''') is arranged, and one or more sets of second nozzles (25''') is arranged downstream the plate. Moreover, the installation further comprises an arrangement (3O7'') for feeding nano particles into the inlet (5''') upstream of an arrangement (31''') for providing a mist to the inlet (5'''), an electrostatic filter section (32' '') provided between the second and third cleaning device (14''', 15''' ), and a device (33''') for gas adsorption provided on the downstream side of the fourth cleaning device (16'').

Description

Scrubber device for gas cleaning

Technical Field of the Invention

This invention relates to an installation for cleaning gases in accordance with the preamble of claim 1.

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 harmful to the health and at times directly life- threatening.

Also exhaust gas from vehicles in tunnels cause environmental problems and it is desirable that the exhaust gas is cleaned at least to some extent and possibly some of the cleaned gas is returned to the tunnel .

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 efficient 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.

A scrubber installation according to the preamble of claim 1 is known from the document WO 98/01213.

Objects and Features of the Invention

The present invention aims at obviating the above-mentioned shortcomings of previously known scrubber installations and at creating an improved installation which can be used for cleaning smoke gases in combination with exhaust gases from vehicles or exclusively exhaust gases from vehicles.

Thus, a primary object of the invention is to create a scrubber installation particularly suitable for cleaning fire gases and/or exhaust gases from vehicles, which installation should not only give an efficient cleaning of gases in respect of solid as well as gaseous constituents such as CO, CO₂, etc., for example, 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 or the exhaust air can be recirculated back to the area from which is was take .

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 Drawings

A non-limiting example of invention will be describer with reference to the drawings, on which: Fig 1 is a schematic illustration of a first embodiment of a known scrubber installation,

Fig 2 is a schematic planar view from above showing a second embodiment of a known scrubber installation, and Fig 3 is a schematic planar view from above showing a scrubber installation according to the invention.

Detailed Description of a Preferred Embodiment of the Invention The background art of the invention will be described with reference to two different known embodiments of an installation for cleaning fire gases shown in Fig 1 and 2.

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. For the specific components forming said scrubber reference is made to 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 to 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 to 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 sprinkler 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 comprising size 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 a second, a third and a fourth cleaning device 14,15,16.

The first or primary cleaning device 13 serves as a preseparator in the scrubber and 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 perforated 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' 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, 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 individual 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 cylindrical shape (bevels may be provided at one of the ends or both) and extend perpendicularly to the plane of the plate.

At a certain distance in front of or upstream the plates 19, 19 ' , a number of pipes extend, each one of which is equipped with a plurality of nozzles. 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', guarantees 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. In the embodiment according to Fig 2, 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 preseparator, 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 substantial difference between the embodiment according to Fig 1 and 2, 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 lattice 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.

An embodiment of the installation according to the invention will now be described with reference to Fig 3. In said embodiment the scrubber 1' ' ' is, in the same way as in Fig 2, located lying or horizontally between an inlet 5' ' ' and an outlet 4''', and comprises at least the same components as in the embodiment shown in Fig 2.

The inventors have found that the efficiency of the installation may be increased if the installation further comprises, seen in the flow direction of the gases:

i) an arrangement 30''' for feeding nano particles into the inlet 5" ' ; ii) an arrangement 31 ^w' for feeding a mist to the inlet 5''', preferably just behind and downstream of the arrangement 30''' for feeding said nano particles;

iii) an electrostatic filter section 32''' provided between the second and third cleaning device 14''', 15''';

iv) a device 33' ''for gas adsorption provided on the upstream side of the fourth cleaning device 16''',

v) possibly a cooling device 34''' arranged on the upstream side of the device 33''' for gas absorption; and

vi) a gas detector 35''' arranged in the outlet 4''' and connected to a computer (not shown) by which it is possible to control the amount of the different liquids, particles and mist fed to the installation as well as the capacity of a fan

The nano particles to be injected in the inlet 5' ' ' comprise a chemical mixture which depends upon the composition of the fire gases/exhaust gases to be treated. The particles may comprise silicate, talcum, kaolin, pyrophyllite, etc. The purpose of the nano particles is to act as on one hand condensation nuclei for impurities in the smoke in the steam phase of the installation, and on the other hand to react chemically with or absorb impurities in the smoke.

The mist is generated by water being ejected under high pressure, of for instance 70-200 bar, from suitable nozzles and in connection with an ultrasound generator, the purpose of this combination is to atomize the water to be injected into the inlet 5' ' ' . Said mist cools the fire gases. In the prior art installations the water droplets have been made by nozzles from which water is ejected only by high pressure. However, by this technique the water droplets formed are relative large, which means that they have a rather poor cooling efficiency. Therefore, by using high pressure in combination with the , ultrasound generator for atomizing the liquid the cooling efficiency can be much increased.

Moreover, in the inventive installation an electrostatic filter section 32''' is provided between the first secondary and second secondary cleaning device 14''', 15'''. The electrostatic filter section 32''' preferably comprises two electrostatic filters. The object of these filters is to eliminate very small particles.

The device 33''' for gas adsorption comprises silica gel preferably in the form of pellets.

In the case the exhaust air of the installation is to be in some extent recirculated to road tunnels, for instance, preferably a cooling devise 34''' is arranged on the upstream side of the device 33''' for gas absorption.

The installation according to the invention is also provided with gas detector 35''' arranged in the outlet duct 36''' and connected to a computer (not shown) . The computer is adapted to control the different components of the installation, such as the amount of the different liquids, particles and mist fed to the installation as well as the capacity of a fan V''. The computer may also control a motor-driven damper 37''' provided in the outlet duct. By the damper it is possible to recirculate part of the exhaust air/gas. Especially, when the installation is adapted for cleaning exhaust gases from vehicles in road tunnels it is possible to make smaller conduits for ventilation if a part of the exhaust air is recirculated, and thus the installation costs will be reduced. As can be seen from Fig 3, the fan η¹¹¹ of the inventive installation is placed in an outlet duct. By providing the fan V'' in the outlet duct of the installation the installation will work with a negative pressure whereby it is possible eliminate the problems with leakage of water in the prior art installations .

The Function and Advantages of the Installation According to the Invention

Before the fire smoke is fed into the installation 1''' by the fan V'' nano particles and water mist are added to the smoke by the arrangements 30''' and 31'''. The smoke then 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 of 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, 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 downstream of the perforated plate by the second nozzles 25'''. Thus, said water is considerably colder than the smoke gas which is fed into the space between the perforated plate and the second cleaning device 14'''.

The solid, relatively small particles which have not been separated from the smoke gas stream will now form nuclei for the water steam which occurs in the space, said water steam condensing and growing together with the particles to larger agglomerates. Said larger agglomerates are relatively simple to separate in the cleaning devices 14''', 15''', 16''' and in the electrostatic filter section 32'''. 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 by the piping system in a fresh, cold state, the water may always solve maximum amounts of gas.

In the second 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 electrostatic filter section 32''' and then 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. Then the gas passes through the device 33''' for gas adsorption containing silica gel.

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, and possibly a part of the gas is recirculated by means of the damper 37'''. Furthermore, by recirculation a part of the gas the supply of fresh air to road tunnels, for instance, can be reduced. This is especially important when the tunnel is very long.

Moreover, by means of the gas detector 35''' provided in the outlet duct 36''' and connected to the computer the exhaust air/gas is monitored and the different components of the installation i' ' ' may be controlled as mentioned above.

Claims

1. Installation for cleaning gases, especially fire smoke gases and/or exhaust gas from vehicles, comprising a scrubber (I' ' ' ) through which the gas may pass from an inlet (5' ' ' ) towards an outlet (4''') and in which a first, second, third and fourth cleaning device (13''', 14''', 15,''' 16''') is included following each other in the direction of the gas flow, of which a first cleaning device (13''') serving as a preseparator includes a perforated plate (19''') upstream of which at least one set of first nozzles (IV'') 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 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''') are arranged downstream 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' ' ' ) , characterized in that the installation further comprises an arrangement (30''') for feeding nano particles into the inlet (5''') upstream of an arrangement (31''') for providing a mist to the inlet (5'''), that an electrostatic filter section (32''') is provided between the second and third cleaning device (14' ' ' , 15' ' ' ) , and that a device (33''') for gas adsorption is provided on the downstream side of the fourth cleaning device (16''') .

2. Installation according to claim 1, characterized in that, in the case some of the exhaust gases are recirculated, a cooling device (34''') is arranged at the downstream side of the device (33''') for gas adsorption.

3. Installation according to claim 1, characterized in that the mist is obtained by water being ejected under high pressure from nozzles in combination with an ultrasound generator (31'''), the purpose of which is to atomize water to be injected into the inlet (5''') of the installation (1''').

4. Installation according to claim 1, characterized in that the water is expelled from the nozzles by using a water pressure of 70-200 bar.

5. Installation according to claim 1, characterized in that a fan (7''') is arranger in the outlet (4''').

6. Installation according to claim 1, characterized in that a gas detector (35'') is arranged at the outlet (4''') connected to a computer by which it is possible to control the amount of the different liquids, particles and mist fed to the installation as well as the capacity of the fan (T'') .