AU672966B2 - Process and plant for exhaust gas purification and a combination of this exhaust gas purification with that of waste water - Google Patents

Description

OPI DATE 26/09/94 AOJP DATE 24/11/94 APPLN. ID 36311/93 111 ii111li II PCT NUMBER PGT/EP93/00502 lii.ii iI iiI i AU933631 1 (51) Internationale Patentklassifikation 5 (11) Internationale Veroffentlichungsnuxnmer: WO 94/20196 BOID 0100 47/2 Al (43) Internationales Verof'entlichungsdaturn: 15. September 1994 (15.09.94) (21) hIternationales Aktenzeichen: PCT/EP93/00502 (81) Bestimmungsstaaten: AU, BG, BR, CA, CZ, F1, JP, KR, NO, PL, RO, RU, SK, UA, US, europiiisches Patent (AT, BE, (22) Internat~onales Anineldedatum: 5. Mhir 1993 (05.03.93) CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT,

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(71) Anmelder (fUr ale Besrimnrungssaren ausser US): VOEST- ALPINE INDUSTRIEANLAGENBAU GMBH [AT/AT]; Veroffentlicht Tunnstrasse 44, A-4031 Linz Mit infernationalem Recherchenbericht.

(72) Erfinder; und Erfinder/Annielder (nur far US): EBERT, Fritz [DE/DE]; Herrenwiesental 16, D-6750 Kaiserslautern B(YITNER, Helmut [DE/DE]; Hochstrasse 12, D-6660 Zweibr~icken KRAlYES, Jblrg [DE/DE]; Gleiwitzerstrasse 8, D-6750 Kaiserslautern GEBERT, Walter Nelkenweg 36, A-4502 St. Marieci PARZERMAIR, Franz [AT/AT]; Waldstrasse 48/32, A-48030 Attnang-Puchheim LANZERSDORFER, Christof 'AT/All; Heiderosenstrasse 26, A-4600 Wels (AT), (74) Anwalte: VON FCTNER, Alexander usw., Mariahilfplatz 2 3, D-8000 Miinchen 90 (DE).

(54) Title: PROCESS AND PLANT FOR EXHAUST GAS PURIFICATION AND A COMIBINATION OF THIS EXHAUST GAS PURIFICATION WITH THAT OF WASTE WATER (54) Bezeichnung: VERFAHREN UND ANLAGE ZUR ABGASREINIGUNG, SOWIE KOMBINATION DIESER ABGASREINIGUNG MIIT EINER ABWASSERREINIGUNG (57) Abstract The invention relates to a process for separating solid and or liquid particles, especially of small diameter, and/or gaseous components from a stream of gas by means of particle separation units, the separation action of which is supported by the use of very finely atomized washing liquid, in that the stream~ of gas is taken to one or more adjacent or successive similar or different particle separation units, into the gas in-tak, of which washing liquid is sprayed in the direction of gas flow immediately in front of the separation unit by means of one or more pneumatic dual-substance nozzles.

(57) Zusammenfassung Die Erfindung betrifft clin Verfabren zur Abscheidung fester und/oder flflssiger Partikel, insbesondere mit kicinem Durchanesser, und/oder gasftbrmiger Komponenten aus einemn Gasstrom durch Partikclabscheideaggregate, deren Abscheidewirkung durch den Einsatz von feinst zerstiiubter Waschfltlssigkeit unterstiltzt wird, indem der Gasstrom einem oder mehreren nebeneinander und/oder nacheinander angeordoeten gleichen oder verschiedenen Partikelabscheideaggregaten zugefiihrt wird, in dessen/deren Gaszuleitung unmittelbar vor demn Abseheideaggregat Waschflilssigkeit mittels einer odee mehrerer pneumatischer Zweistoffdflsen in Gasstrdmungsrich-,ung eingedtlst wird.

1 Method and system for cleaning exhaust gases, as well as the combination of this exhaust-gas cleaning with waste-water purification The invention relates to a method and one or a plurality of systems for separating solid and/or liquid particles with small diameters and/or gaseous components from a gas flow by means of very finely atomized washing fluid. In order to fulfil the widespread demand for waste-water-free operation of exhaust-gas cleaning systems, multistage recirculation-fluid processing is integrated in the method.

The invention is suitable in particular for improving the separation efficiency of existing inertia particle separators or washers in the fine-dust range by simple extension in accordance with the invention.

Conventional inertia particle separators such as, for example, cyclones and baffle separators have only low separation efficiency for particles in the lower micron and submicron ranges. This also applies to conventional washers such as rotary washers and low-pressure venturi washers.

Particle separators which operate wet are based on the principle that very small particles which, owing to the small gravitational force, can no longer be separated with conventional inertia separators, are enlarged by the addition of fluid.

The drop thus formed by the fluid and the particle to be separated is generally large enough to be removed from the gas flow without problems. A particle separator which operates wet therefore always consists of a region in which drops and particles can interact with one another and a region in which the drops are separated, even if as in this invention with the use of a cyclone, the two regions are in practice not spatially separated from one another.

Moreover, in a cyclone dust separator known from DE-PS 30 18 162, the washing-fluid inlet is disposed above the gas outlet of an inner chamber, as a result of which the exhaust gas escaping dry from the inner separation chamber is taken to the outer separation chamber for the separation of the finest dust particles still present therein and, at the same time, is moistened. The moist dust particles separated are carried away from the outer separation chamber. Fine dust particles which are still present in the exhaust gas, which is cleaned to a large extent in the inner chamber, 3 are thus washed out before the exhaust gas is drawn off.

DE-OS 32 42 651 describes a method of separating dry flue ash from a hot gas at 100 to 2000 0 C, in which most of the flue ash is first separated by a cyclone and the gas is then washed in at least two stages. Some of the aqueous flue ash suspension obtained in the first stage is injected into the original gas in a position before the cyclone in order to increase the efficiency of the cyclone by reducing the temperature of the crude gas. The cyclone itself serves as a dry separation step.

In this case, however, the gas is never cooled below the dew point and the product is obtained dry.

In DE-PS 30 49 752 a dust separator is described in which kinematic coagulation at high speed in a gas-duct restriction and centrifugal separation take place simultaneously. The fluid is supplied into the !rude-gas inlet of a cyclone. After the supply point, the inlet pipe, which is already bent, becomes narrower in order to become wider again like a diffusor just befor the entry to the cyclone. In this case, the fluid is supplied either by means of a sprinkler mounted in the inlet pipe or by means of openings disposed inside 7 4 the inlet pipe and extending over the entire cross-section.

A gas cleaner known from US-PS 3,696,590 has a plurality of quenching nozzles in its inlet.

After the admission of moisture, the gas flow is deflected in a 90 0 C bend and passes a turbulence damper before it enters the cyclone. The individual nozzles can be pressurized separately from one another.

It is known that a high relative speed between a drop and a particle to be separated increases the probability of the particle meeting the drop.

This principle is used in venturi washers. The gas flow is accelerated to high flow rates by means of a reduction in cross-section. The washing fluid is added at the narrowest cross section.

Owing to the high flow rate, the water flow separates into fine drops which are then accelerated in the gas flow until they also have the speed of the gas. The smaller the drops are, the faster they reach this speed and the shorter, consequently, is the time during which an appreciable relative speed exists between the drops and the particles. On the other hand, the probability of a particle meeting a drop increases obCl~ r with decreasing drop diameter for a given quantity of washing fluid.

Thus DE-PS 23 05 710 describes a venturi washer with a central axial insert body. This washer comprises two zones in which a relative movement between the fluid drops and the gas leads to intensive contact between the media, which favours washing efficiency.

A wet separator known from DE-PS 21 16 482 consists of a venturi tube in the neck of which an atomizer nozzle for water is disposed. This is connected to a centrifugal separator. The solid particles are weighted by the fluid injected and are thrown off tangentially by the built-in spinning member.

A disadvantage of these washers is the large pressure drop which has to be compensated for by the blower output.

Moreover, methods are known in which the fluid is atomized by means of rotating baffles (discs, drums, etc.). This inevitably results in relatively high equipment and maintenance costs.

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7-01 6 In a device and a method described in US-PS 4,067,703, the interaction space consists essentially of a tube the diameter and the length of which are arranged in a manner such that tube turbulence as well as a relatively long contact time between the particles and the fluid drops arise. The washing fluid is split up very finely in the gas-flow to be cleaned by means of a double nozzle. The drops loaded with dust are separated in a separator which is mounted around a centrifugal blower. The nozzle is disposed in the gas flow, a minimum distance having to be kept between the nozzle and the blower, so that the atomizing cone completely fills the interior of the pipe. The spray zone is associated with the low-pressure blower which not only serves for advancing the gas flow but extends the contact space for the impaction of the particles beyond the region of the tube. This blower is intended, at the same time, to favour the coalescence of the water drops. The water flows within the blower through a pipe with a water seal into a slurry tank.

Like the methods with rotating baffles described above, this method also has the same disadvantages of relatively high equipment and maintenance R, ~costs.

7 7 PCT/AT 91/00077 describes a method and a system for cleaning gases with a large washing tower which is equipped with double nozzles. These nozzles are distributed over the entire cross section of the washer and can be supplied separately with atomizing gas and washing fluid.

A corresponding quantity of washing fluid is thus introduced evenly over the entire gas-flow cross section.

DE-GM 82 18 483 describes a cyclone into the outlet pipe of which washing fluid is injected.

The outlet pipe is thus formed as a washer. This arrangement does not relate, however, to a useful drop separation.

Moreover, in a known method of removing dust from exhaust gases of ore-processing, sintering and/or pelletizing works, at least some of the dust is subjected to processing in a wet-chemical process and the waste water of the process is subjected to cleaning. This method is intended to subject metal compounds, amongst other things, as they are present in dusts of this type from the exhaust gases of the process, to reutilization. At the same time, this method is intended to produce process wastG water of the highest degree of purity, suitable for subsequent recirculation as j~

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-8washing fluid or for the production of slurries. For this purpose, the gases to be cleaned are washed with washing fluid at a pH of from 0 tO 10, the reduction of the dusts to slurry is regulated at pH 3 to 5, and the solids are filtered off, whereupon the filtrate is subjected to heavy-metal precipitation and the precipitate is separated. There then remains a solution which contains essentially only alkali halides and which can be taken into circulation.

In accordance with one aspect of the present invention there is provided a method of separating solid and/or fluid particles, particularly with small diameters, and/or gaseous components from a gas flow by means of one or more particle-separation units, the separating efficiency of which is assisted by the use of very finely atomized washing fluid, characterized in that said method comprises supplying the gas flow to one or more similar or different particle-separation units which are disposed side by side and/or one after another and injecting washing fluid into gas inlets of the said one or more similar or different particle-separation units in the direction of the gas flow, immediately before said one or more similar or different particleseparation units, by means of one or more nozzles for pneumatically mixing two components, the speed of the washing fluid leaving the said one or more nozzles being faster than the speed of the gas flow.

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-I In accordance with another aspect of the present invention there is provided a system for carrying out the aforesaid method, characterized in that the system comprises one or more nozzles disposed immediately upstream of each particle-separation unit to inject the washing fluid into the gas flow, in the direction of the gas flow, in very finely-divided form, each nozzle being supplied separately with atomizing gas and washing fluid.

The embodiments to be presently described herein include systems for carrying out the method which are distinguished by their compact 0.00 aa construction. The embodiments also describe a method of the present i 0 invention which is particularly suitable for integration by simple refitting in existing inertia particle separators or washers, thus decisively improving their separation efficiency for these extremely fine particles.

oe 0 0° Moreover, waste-water-free operation of the embodiments of the system to .oo, be described herein is possible because of the processing of the washing 15 fluid, the expenditure necessary for the processing of the washing fluid discharged and for the disposal of the solid residues being minimized by the construction of these embodiments and valuable substances contained in the washing fluid at the same time being recoverable, Furthermore, the embodiments of the method and system for carrying out the method of the present invention, to be described herein, provide that in I

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-9.1 addition to the normal dust particles and waste gases, extremely fine particles with a particle size of less then 1.0 rtim are also separated more efficiently than is possible with conventional methods and the washing-fluid 'I drops injected for this purpose are completely removed again from the gas r 5 flow.

*49r _S tA.) LIt VNVt 0c Embodiments of the invention are described in greater detail below with reference to the drawings, in which: Fig. 1 shows a first embodiment of a system for carrying out the method according to the invention with a tangential-flow cyclone as the particleseparation unit; Fig. 2 shows the unit II of Fig. 1; Fig. 3 shows a second embodiment of a system for carrying out the method according to the invention with a venturi washer as the particle-separation unit; Fig. 4 shows a third embodiment of a system for carrying out the method according to the invention with integrated processing of the washing fluid; Fig. 5 shows a separation curve indicating the effect of the double nozzle on the separation result; Fig. 6 shows a separation curve of the system of Fig. 1 with a pneumatic double nozzle with internal mixing.

i With the system shown in Fig. 1, the crude gas flow reaches the cyclone through a tube and the cyclone inlet Or, this route, the crude gas flow is enriched with washing water drops which are produced by one or more nozzles for pneumatically mixing two components (Fig. also referred to herein as two component mixing nozzles. Since the drops, which are injected as a parallel flow, leave the nozzle outlet region at a speed faster than the speed of the crude gas, particles can be deposited on the drops, by virtue of inertia effects. When the spray reaches the 4cyclone, it is deflected in accordance with the flow conditions in the cyclone. In the region of the cyclone inlet the fine particles preferably have an increased probability of meeting the drops since, according to inertia, these particles can adapt more easily to the fluctuating movements of the turbulent gas flow than larger particles. The effectiveness of this turbulent .090 agglomeration, which is not limited solely to the cyclone inlet region but is effective throughout the cyclone, depends, on the one hand, ooo on the flow conditions within the cyclone and, on the other hand, nor :as is clear from separate tests on the quality of the atomizing device, that is, on the set of drops produced.

12 When this three-phase mixture of carrier gas, drops and particles to be separated enters the space inside the cyclone, the large drops are deposited on the cyclone wall owing to the large centrifugal force in the cyclone. On the way to the cyclone wall naturally, further particles are deposited on the drops.

This process is more efficient the more drops enter the space inside the cyclone. In the space inside the cyclone, the fine particles are deposited on the drops, owing to the interaction induced by the turbulence already mentioned. The particles separated with the drops are transported by the cone boundary-layer flow in the cyclone, on the inner wall, towards a bin An apex cone in the bin serves mainly for stabilizing the turbulence. It is also intended, however, to prevent the drops from re-entering the gas flow.

The gas flow leaves the cyclone through an immersed pipe After the cyclone en the clean-gas side the gas flow is free of drops. The4 oe O x nozzles in the inlet pipe of the cyclone are preferably operated in the range from 3.0 to 9.0 bars.

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In the system shown in Figure 3, the crude gas flow reaches the venturi duct (14) through a tube (12) and a converging venturi inlet On this -13route, the crude gas flow is enriched with very fine washing-fluid drops which are produced by one or more two component mixing nozzles Since the fine drops, which are injected in a parallel flow, leave the nozzleoutlet region at a speed faster than the speed of the gas, the particles are deposited on the drops, owing to inertia effects and by turbulent diffusion.

In the converging venturi inlet the gas flow, with the fine washing-fluid drops it contains, is then accelerated. In the venturi duct (14) and in the subsequent diverging venturi outlet, these fine drops and the particles still contained are separated by the washing fluid (16) introduced into the ;«Ui 10 venturi duct. This construction enables very fine particles to be separated advantage of this construction lies in the fact that it is possible to compensate for the dependency of the separation effectiveness of venturi washers on the quantity of gas put through by appropriate adaptation of the operating parameters of the two component mixing nozzles such that, when the separation effectiveness of the venturi washer falls because of reduced gas throughput, the additional separation is made good by the two component mixing nozzles, for example, by increased nozzle pressure.

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li 14 The third embodiment of the system shown in Fig. 4 comprises a saturation stage two particleseparation stages and integrated waste-water processing (20) to (24) which, in principle, can also be integrated in the method in the same manner in the other embodiments. This construction permits waste-water free operation.

In this configuration, the method is suitable, for example, for removing dust from sintering exhaust gases. The gas flow first of all reaches a quencher (17) where it is saturated, in known manner, by the injection of fluid as a counterflow (25) and/or as a parallel flow and/or as a cross-flow The difference between the vapour pressure of the washing fluid in the gas flow entering in comparison with the saturation vapour pressure of the washing fluid in the inlet condition is intended to be small so as not to vaporize too many of the fluid drops. In order to distribute the flow evenly, a drop separator on the output side, with cleaning nozzles is disposed directly in front of a following nozzle plane (28) of the respective particle-separation stage which, in this case, is formed as an axialflow multiple cyclone In this case, the nozzle lances on which theou 010, nozzles are mounted are advantageously formed in a 1;Lr 0 D manner such that each individual cyclone is J -\LWO COwA KC A W' kc<'v associated with one/dote ozzle..

i A subsequent particle-separation stage (30) is t formed as a plate separator. With the use of a plate separator, surface-covering admission of the fluid drops to the plate separator must be ensured by the distance between the nozzles and the plate separator. In this connection, the spray angle of the nozzles is of particular importance. The arrangement, the geometry and the operating parameters of the ettte/ ozzles are preferably selected in a manner such as to achieve as short as possible a flight time of the drops before the particle separator, preferably considerably less than one second. A further drop separator with cleaning nozzles (31) may be mounted in the gas outlet of the washer in order to separate the finest drops still present in the gas flow.

The fluid ciriuits of the three units connected one after another are separate from one another, the regeneration of all of the quantities of fluid evaporated and all of the quantities of fluid discharged from the process in order to remove dissolved material taking place, according to the invention, only in the last stage of the system, f in the direction of the gas flow, through a fluid 7S i t I b"1 j ^og7 supply From this stage, a portion of the fluid taken in circulation by means of the sedimentation stage (33) is supplied to the upstream stage (at 34). The fluid circuits of this stage, and of the saturation stage, are similarly constructed with sedimentation stages and (36) and outputs (37) and (38) into the saturation stage or a waste-water purification system. This construction ensures that the concentration of the dissolved substances increases in the direction contrary to the gasflow in the fluid circuits of the stages of the system. This permits a reduction in the construction size of waste-water purification equipment and crystallization stages, the concentration of the dissolved substances in the fluid circuit of the last stage of the system in the direction of the gas flow simultaneously being kept low, so that a discharge of separated substances by means of the slight breakage of the extremely fine drops produced by thepem.

etiae nozzles remains minimal.

Moreover, the separation of the fluid circuits enables various characteristics of the circulation fluid such as, for example, the pH value and the chemical composition in the individual circuits to Rs. Ait" be adjusted in dependence on the predetermined

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Noc~a i -Fu i7 separation requirements given by the gas flow and particles.

If a comparatively high proportion of dissolved salts such as, for example, calcium chloride, arises in the fluid circuit of the first stage according to the invention, the concentration of the salts is kept just below saturation point by suitable adjustment of the discharge quantities (34) and A partial flow of the circuit fluid is then taken, in a separate circuit, through a cooled crystallization basin (39) in which a portion (40) of the crystals recovered is implanted improve crystallization.

The salt thus recovered can be supplied for utilization. These measures enable the quantities of fluid (38) which have to be removed from the circuit in order to discharge heavy metals and other dissolved waste substances to be further reduced.

Precipitation chemicals (41) such as milk of lime, caustic soda, sodium sulphide, etc. and, occasionally, residues mostly waste which is difficult to dispose of and which still contains valuable substances, for example, filter dust from a dry filter are added to the first precipitation stage (20) of the waste-water 18 purification equipment in addition to the discharged circuit fluid, a selective precipitation of valuable substances taking place, according to the composition of the dissolved substances contained in the fluid, by precise adjustment of a pH value or by the addition of selective precipitation agents. The valuable substances precipitated out, for example, in the purification of sintering exhaust gases :iron precipitation at pH 3 to 5 are separated (see 21) and supplied for utilization and the supernatant liquid is supplied to the heavy-metal precipitation stage (22).

A portion of the supernatant liquid (42) of the first precipitation stage is recirculated to the fluid circuit of the last particle-separation stage The pH value of the fluid is adjusted to the desired value by this recirculation (42).

In the heavy-metal precipitation stage (22) the heavy metals content is precipitated out by the further addition of precipitation chemicals (43).

The h 1 iry metals are separated (see 23) and, if there is no further use for the supernatant liquid, it is supplied to a crystallization stage S(24) upstream of which a double decomposition stage in which, for example, calcium ions S are separated by the addition of sodium carbonate or carbon dioxide, is occasionally disposed, in order to recover pure salts. The separated calcium carbonate suspension is then recirculated to the first precipitation stage In the crystallization stage the dissolved substances are wholly or partially crystallized out, in the case partial crystallization, the remaining concentrated fluid being recirculated into the fluid circuit of the saturation stage.

If undesired trace substances which are not separated out in the precipitation stages become concentrated in the system, a small quantity of fluid is removed from the crystallization stage (see 45) and has to be vaporized or treated in a suitable manner for disposal.

The atomization method used is of particular importance for the particle separation. In the system shown in Figs. 1 to 4, the/ lea nozzles used are operated with compressed air and circulation fluid, for example, water or high boiling organic liquid. For this purpose, p Le l6-1nozzles with external or internal mixing are used. In the nozzles with external mixing, the fluid flow and the compressed-air flow can be varied separately from one another.

Limiting factors for operation are simply the pressure drop at the gas or fluid outlet. With the nozzles with internal mixing, the gas and fluid flows influence one another. The nozzles used with internal mixing are distinguished by a high degree of mixing already within the nozzle body and an optimized jet-outlet geometry. The preliminary dispersion of the liquid and gaseous phases thus created has a lower critical speed than the individual phases. Smaller friction and acceleration losses thus occur than with nozzles with external mixing. These nozzles therefore have a considerably better energy utilization than conventional atomization devices (for example, single pressure nozzles) in some of which more than 99% of the pressure energy is converted into kinetic energy.

The effect on the separation result can be seen from test results which are shown in Fig. 5. The operating parameters of the tests recorded by the curves (particle separation unit: tangentialflow cyclone) were as follows: Quantity of exhaust gas in normal conditions 1200 m3/h Water requirement L/G: 0.2 l/m3 Exhaust gas temperature: 20 C A<i Nozzle with internal mixing: 4.8 bars absolute -T 0f1roQ 21 Nozzle with external mixing: 6.3 bars absolute The nozzle with internal mixing was never operated at the compressed air pressure of 5.0 to which, according to experience, is advantageous, in order to permit comparison with the nozzles with external mixing. Other tests also showed that the success of the separation is connected directly with the quality of the atomizer device, that is, with a nozzle with internal mixing. If the system shown in Fig. 1 is operated with the use of a~ enozzle with internal mixing under the favourable conditions according to the invention: Quantity of exhaust gas in normal conditions: 690 m3/h Water requirement L/G: 0.25 l/m3 Crude gas concentration: 204.9 mg/m3 Nozzle with internal mixing: 5.07 bars absolute the separation curves shown in Fig. 6 are achieved. The separation capability of the system according to the invention shown in Fig. 1 was checked both with an optical particle counter and with a gravimetric method of measurement according to VDI (Verein Deutscher Ingenieure Association of German Engineers) guideline 2066. In the case C B""fizro 22 shown, the overall separation efficiency was 99.2%.

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Claims (5)

1. Method of separating solid and/or fluid particles, particularly with small diameters, and/or gaseous components from a gas flow by means of one or more particle-separation units, the separating efficiency of which is assisted by the use of very finely atomized washing fluid, characterized in that said method comprises supplying the gas flow to one or more similar or different particle-separation units which are disposed side by side and/or one after another and injecting washing fluid into gas inlets of the said one or more similar or different particle-separation units in the direction of the gas flow, immediately before said one or more similar or different particle-separation units, by means of one or more nozzles for pneumatically mixing two components, the speed of the washing fluid o leaving the said one or more nozzles being faster than the speed of the gas flow. o* 4990 15 2. Method according to Claim 1, characterized in that a tangential-flow cyclone, an axial-flow cyclone, or a tangential- or axial-flow Smultiple cyclone is used as a particle-separation unit.

3. Method according to Claim 1, characterized in that an inertia separator, preferably a baffle separator, a plate separator or an annulr- gap separator, is used as a particle-separation unit.

24- 4. Method according to Claim 1, characterized in that a washer, preferably a venturi washer, a vortex washer or an annular-gap washer, is used as a particle-separation unit. Method according to any one of Claims 1 to 4, characterized in that in order to break up the fluid, a said nozzle, with internal or external mixing of fluid and atomization medium, particularly compressed air, compressed gas, or steam, is preferably provided with internal mixing. 6. Method according to any one of Claims 1 to 5, characterized Sin that the gas flow to be cleaned is saturated with fluid before the washing 10 fluid is introduced. 7. Method according to any one of Claims 1 to 5, characterized in that the operating parameters of the nozzles, particularly the nozzle pressure, are controlled in dependence on the separation efficiency of the t lt particle-separation unit and on the quantity of gas throughput. t I 8. Method according to Claim 1, characterized in that pulverized solids which bind waste substances are added to the gas flow before the input to the saturation stage or the first particle-separation stage, or to the circulation washing fluid of the saturation stage. .LRA, I1 9. Method according to any one of claims 1 to 8, characterized in that multi-stage circulation-fluid processing in which the individual fluid circuits of each particle-separation unit are completely separate from one another, is integrated in the gas purification system. 10. Method according to Claim 9, characterized in that a sedimentation stage is connected in one or in each of a plurality of the separate fluid circuits to separate the undissolved particles contained. 11. Method according to Claim 9 or Claim 10, characterized in that the concentration of dissolved substances in the circulation fluids of successive stages of the method increases in the WOO ~AT O0 "IVT 0" Li 1 I direction contrary to the gas flow owing to controlled fluid,/44eQ4 in the respective upstream stage, by making up evaporated fluid solely in the last particle-separation stage in the direction of flow of the gas, and by discharging fluid in order to discharge dissolved substances solely from the first stage of the method. 12. Method according to any one of Claims 9 to 11, characterized in that the concentration of dissolved salts in the first stage in the direction of flow of the gas is kept just below the solubility limit and chat a portion of the circulation fluid of this stage is taken into the circuit by means of a cooled crystallization basin. 13. Method according to Claim 12, characterized in that the quantity of fluid discharged in order to remove dissolved substances is processed by a multi-stage process in which the valuable substances and heavy metals dissolved in the fluid are precipitated out and recovered one after another by the controlled addition of precipitation chemicals in a plurality of stages. 27 14. Method according to Claim 13, characterized in that, in addition, further residues containing valuable substances are added in one or a plurality of precipitation stages for processing. Method according to Claim 13, characterized in that a portion of the supernatant liquid from the first precipitation stage is taken to the fluid circuit of the last particle- separation stage in the direction of flow of the gas in order to set the desired pH value of the circulation fluid. 16. Method according to Claim 13, characterized in that the supernatant liquid of the last precipitation stage is supplied to a crystallization stage in order to recover the dissolved salts, a partial evaporation with recirculation of the remaining fluid to the fluid circuit of the saturation stage or the first particle-separation stage, or a complete evaporation of the supernatant liquid being carried out, alternatively, 17. Method according to Claim 16, Scharacterized in that, a suitable double Sdecomposition stage, preferably a precipitation of 2 -28- calcium carbonate with carbon dioxide or a soluble carbonate with recirculation of the calcium carbonate suspension recovered to the first precipitation stage, is disposed before the crystallization stage. 18. Method according to Claim 13, characterized in that the supernatant liquid of the last precipitation stage is supplied to a spray drier. I 19. System for carrying out the method according to any one of Claims 1 to 8, characterized in that it comprises one or more nozzles disposed immediately upstream or each particle-separation unit to inject the washing fluid into the gas flow, in the direction of the gas flow, in very finely-divided form, each nozzle being supplied separately with atomizing gas and washing fluid. 20. System according to Claim 19, characterized in that one or more nozzles is disposed in a nozzle plane which is preferably perpendicular to the direction of the gas flow or said nozzles and/or nozzle planes are disposed one behind another L i 29 and/or spatially offset in the gas inlet of the particle-separation unit. 21. System for carrying out the method according to any one of Claims 9 to 18, characterized in that each particle-separation stage 4- is connected to a multi-stage circulation-fluid processing device, and in that the individual circulation-fluid processing devices are completely separate from one another. 22. System according to Claim 21, characterized in that a respective sedimentation stage 3-3, -35 -36- is fitted in one or a plurality of the separate fluid circuits. 23. System according to Claim 21, characterized in that a cooled crystallization basin is provided for a portion of the circulation fluid in the first circulation-fluid processing device in the direction of the gas flow. 24. System according to any one of Claims 19 to 23, characterized in that a quencher 417 is used to saturate the gas flow with fluid before the first nozzle or nozzle plane *28. f R System according to Claim 24, characterized in that the drop separator disposed in the gas outlet of the quencher is disposed directly before the first nozzle or nozzle plane of the following particle-separation unit so that, advantageously, a very even gas flow is created tor this nozzle or nozzle plane.

26. A method of separating solid and/or fluid particles, particularly with small diameters, and/or gaseous components from a gas flow substantially as hereinbefore described.

27. A system for separating solid and/or fluid particles, particularly with small diameters, and/or gaseous components from a gas flow substantially as hereinbefore described with reference to the accompanying drawings. Dated this THIRD day of SEPTEMBER 199. VOEST-ALPHINE INDUSTRIEANLAGENBAU GESELLSCHAFT Applicant Wray Associates Perth, Western Australia Patent Attorneys for tho Applicant 31 Method and system for cleaning exhaust gases as well as the combination of this exhaust-gas cleaning with waste water purification Abstract The invention relates to a method of separating solid and/or fluid particles, particularly with small diameters, and/or gaseous components from a gas flow by means of particle-separation units, the separation efficiency of which is assisted by the use of very finely atomized washing fluid, in which the gas flow is supplied to one or a plurality of similar or different particle separation units which are disposed side by side and/or one after another and into the gas inlets of which washing fluid is injected in the direction of the gas flow, immediately before the separation unit, by means of one or a plurality of pneumatic double nozzles.