AU710611B2 - Process and apparatus for separating polycyclic and polyhalogenated hydrocarbons from exhaust gas of a sintering process - Google Patents

Description

Background of the Invention This invention relates to a process and an apparatus for separating polycyclic and polyhalogenated hydrocarbons, particularly polyhalogenated dibenzodioxins and dibenzofurans, from the exhaust gas of a sintering process, particularly a process of sintering iron ore.

Fine-grained or pulverized materials can be compacted by sintering to provide shapes, such as granules and pellets, which can more easily be handled.

Sintering is used, to compact ores. For that purpose the fine-grained ore is mixed with fine-grained Scarbonaceous fuels, is agglomerated and is heated to temperatures above 1000 0 C in sintering plants supplied with oxygen-containing gases. The agglomerates of sintered ore consist of granules or pellets and have a certain mechanical strength so that they can readily be reduced to metals, in blast furnaces. Sinter roasting is used to roast fine-grained sulfide ores and to process them at the same time to form sintered granules and pellets.

-2- -7 Sintering involves a decomposition, particularly of carbonates and sulfates, an oxidation of sulfides, an evaporation of readily volatile oxides, sulfides, and chlorides, and an expulsion of bound water. As a result, the exhaust gases formed in the sintering process contain the gaseous reaction products CO and CO 2 formed by the combustion of carbon and the gaseous pollutants which have been released from the ores.

Since halogenides, particularly chlorides, as well as carbon are present during the sintering process, polycyclic and polyhalogenated hydrocarbons and particularly polyhalogenated dibenzodioxins (PCDD) and polyhalogenated dibenzofurans (PCDF) are formed, which are contained in the exhaust gas stream leaving the sintering plant. Finally, the exhaust gas stream from the sintering process is contaminated with dust-like solid particles. The gaseous pollutants, particularly CO, SO 2 HC1 and HF, as well as the dust and the polycyclic and polyhalogenated hydrocarbons, S" particularly the polyhalogenated dibenzodioxins and dibenzofurans, must be separated from the exhaust gas before it is discharged into the atmosphere.

Published German Patent Application 41 05 214 discloses the purification of the exhaust gas stream from a sintering plant in a process in which the exhaust gas stream withdrawn from sintering conveyors is dedusted in an electrostatic precipitator plant, the exhaust gas stream leaving the electrostatic precipitator plant is moistened with a finely dispersed aqueous treating solution, which contains hydrogen peroxide, the exhaust gas stream is subsequently fed to a scrubber, which contains a corona electrode assembly and a succeeding scrubbing zone, wherein the exhaust gas stream which has been moistened and has been conducted through the corona electrode assembly in a dropless state is contacted in the scrubbing zone of the scrubber with a finely dispersed scrubbing liquid, which contains finely ground activated carbon or finely ground hearth furnace coke. In an alternative of the known process, the moistened exhaust gas stream which has been S* conducted through the corona electrode assembly in a dropless state is contacted in the scrubbing zone of the S. scrubber with a finely dispersed scrubbing liquid, which is conducted in a scrubbing liquid circuit and before entering the scrubber is passed through an activated carbon filter or a bed of granular hearth furnace coke.

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Published German Patent Application 41 13 597 discloses for the purification of exhaust gas a process in which dust, HCl, HF, SO 2 and optionally NOx are removed and pollutants, particularly dioxins and furans, are removed by adsorption by an adsorbent, which consists of zeolites having a Si0 2 -to-A1 2 0 3 mole ratio of 2 to 6. In that process it is also contemplated that the exhaust gas is first mixed with the zeolites and is subsequently passed through a cloth filter, which contains a filter layer, and 30 to 700 mg zeolites having a particle diameter of 1 to 100 micrometers, particularly of 5 to 20 micrometers, are supplied to the exhaust gas per m 3 thereof.

Published German Patent Application 40 12 982 discloses for the purification of gases and exhaust gases to remove inorganic and organic pollutants a process in which finely powdered activated alumina, silica gel, diatomite, finely powdered zeolites and/or similar inorganic substances are blown into the gas stream, gas and solids are intensely mixed, the solids are applied to a filter surface and are left on the oooeQ S filter as a renewable loose adsorbent layer having a sufficient depth, and the pollutant-laden solids are

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mechanically removed from there. In the known process it is contemplated to use the inorganic surfactants in the form of a finely powdered material having a particle size distribution in which 100 of the particles are less than 100 micrometers, preferably less than micrometers. That process is to be used, inter alia, to separate dioxins and furans.

Published German Patent Application 41 28 106 describes the selective separation of highly condensed polycyclic hydrocarbons, particularly of halogenated dibenzodioxins and dibenzofurans, from previously dedusted exhaust gases, which contain SO 2

H

2 0, and heavy metals, in a process in which the hydrocarbons are adsorbed on solid adsorbents, which consist of a dealuminized zeolite, which has an SiO 2 /A1 2 0 3 ratio from 20:1 to 1000:1; when the adsorption is effected at a temperature from 20 to 200 0 C; the zeolite has a particle diameter from 1 to 5 mm and is contained in a fixed bed reactor or a moving-bed reactor.

*6 German Patent Application P 44 03 244.7 discloses for the purification of oxygen-containing exhaust gases formed by the incineration of garbage, industrial waste materials, and sewage sludge a process in which polyhalogenated hydrocarbons, inter alia, are removed from the exhaust gases by adsorption on zeolites, the exhaust gases above their dew point are reacted at a temperature from 80 to 180 0 C and a gas velocity from 3 to 20 meters per second with a mixture of naturally occurring zeolites in a gas-solids suspension for a reaction time from 0.5 to 10 seconds, wherein the median particle size of the mixed zeolites is from 5 to micrometers and the mean suspension density of the gas-solids suspension is from 0.02 to 10 kg solids per sm 3 of exhaust gas (sm 3 standard cubic meter of dry gas).

Finally, German Patent Application P 44 13 280.8 discloses the separation of polyhalogenated dibenzodioxins and dibenzofurans from the exhaust gas from a sintering process, particularly a process of sintering iron ore, in a process in which the entire -7

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dust-containing exhaust gas from the sintering conveyor is contacted above the dew point at a temperature from to 180 0 C and at a velocity from 6 to 20 meters per second with a mixture of naturally occurring zeolites in a gas-solids suspension for a reaction time from 0.5 to seconds, wherein the median particle diameter of the mixed zeolites is from 5 to 100 micrometers, the mean suspension density of the gas-solids suspension is from 5 to 4500 g solids per sm 3 exhaust gas, the dust and the mixed zeolites are subsequently jointly separated from the gas-solids suspension, and part of the separated solids are again contacted with the exhaust gas from the sintering conveyor. That known process is carried out in an apparatus which consists of a solids-entraining reactor, a multifield electrostatic precipitator, and a solids recycle line, which connects the collecting space of the first field of the electrostatic precipitator or the collecting spaces of the first and second fields of the electrostatic precipitator to the exhaust line leading to the solids-entraining reactor. In that apparatus the o electrostatic precipitator may be replaced by a bag filter.

-8- 9 An object of the present invention is to overcome or at least substantially ameliorate at least one of the problems mentioned in the above prior art, and it is not necessary that the invention in its broadest aspect, should overcome or address each and every one of the above problems in the prior art.

SUMMARY OF THE INVENTION According to the present invention, there is provided a process of separating polysyclic and polyhalogenated hydrocarbons from an exhaust gas of a sintering process, said exhaust gas containing dust and said process including the steps of bringing the entire exhaust gas from the sintering process into contact with a solid adsorption agent selected from the group consisting of clays, layer silicates, diatomaceous earth and mixtures thereof within a gassolids suspension for a reaction time of from 0.5 to 10 seconds above a dew point of the exhaust gas at a temperature from 90 to 1800C and at a velocity from 6 to 20 metres per second; subsequently separating said solid adsorption agent and said dust jointly from the gas-solids suspension to form separated solids and contacting said exhaust gas from the sintering process with a part of the separated solids; wherein said solid adsorption agent has a median particle diameter, d 50 of from 5 to 100 micrometers and the gas-solids suspension has a mean suspension density of from 5 to 500 g solids per sm 3 of said exhaust gas.

The clays may include kaolinite, bentonite, illite and mixtures thereof.

The process may further include admixing from 2 to 5% by weight of activated carbon with said solid adsorption agent prior to the bringing of the exhaust gas into contact with the solid adsorption agent.

The process may further include admixing from 10 to 40% by weight of a S 25 mixture of naturally occurring zeolites the clays with said solid adsorption agent prior to the bringing of the exhaust gas into contact with the solid adsorption agent.

wihThe zeolites may consist of 10 to 20% by weight mordenite, 60 to 70% by •weight clinoptilonite, 0 to 5% by weight montmorillonite, with a balance consisting of SiO 2

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The polycyclic and polyhalogenated hydrocarbons may include polyhalogenated dibenzodioxins and dibenzofurans.

The sintering process may be a process of sintering iron ore performed in a sintering apparatus having a sintering conveyor.

According to another aspect of the invention, there is provided an apparatus for performing the above described process wherein said apparatus includes: means for bringing the entire exhaust gas from the sintering process into contact with a solid adsorption agent within a flowing gas-solids suspension, wherein said means for bringing said entire exhaust gas into contact with the solid adsorption agent includes a solids-entraining reactor; *means for subsequently separating said solid adsorption agent and said dust jointly from the gas-solids suspension to form separated solids, wherein said means for subsequently separating includes a multifield electrostatic precipitator having at least a first and second collecting space in respective first and second fields thereof; and means for bringing said exhaust gas from the sintering process into contact with a part of the separated solids including a solids recycle line connecting at least one of said collecting spaces with an exhaust gas line conducting said exhaust gas from said sintering process.

According to a further aspect of the invention, there is provided an apparatus for performing the above described process wherein said apparatus includes: means for bringing the entire exhaust gas from the sintering process into contact with a solid adsorption agent within a flowing gas-solids suspension, wherein said means for bringing said entire exhaust gas into contact with the solid adsorption agent includes a solids-entraining reactor; means for subsequently separating said solid adsorption agent and said dust jointly from the gas-solids suspension to form separated solids, wherein said means for subsequently separating includes a bag filter having a collecting space; and 11 means for bringing said exhaust gas from the sintering process into contact with a part of the separated solids including a solids recycle line connecting said collecting space of the bag filter with an exhaust gas line conducting said exhaust gas from said sintering process.

BRIEF DESCRIPTION OF THE DRAWING In order that the invention might be more fully understood, embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which: C C C

CC..

C

C..

C.

C

C.

NEXT PAGE IS PAGE 17 I II EDITORIAL

NOTE

NUMBER 40256/95 THIS SPECIFICATION DOES NOT CONTAIN PAGES NUMBERED 12,13,14,15 OR 16.

The sole figure is a diagrammatic view of an apparatus for performing one embodiment of the process according to the invention.

Description of the Preferred Embodiments The sintering machine 1 consists of a sintering conveyor C and is used to make iron ore pellets P from agglomerates, which contain fine-grained iron ore 0 and fine-grained coke F. The iron ore pellets P are then fed to a blast furnace B. Exhaust gas E is fed at a rate of about 5000 sm 3 /h from an exhaust gas hood 2 of the sintering conveyor C to the heat exchanger 3, in which the exhaust gas E is cooled to about 200 0 C. The exhaust gas then enters an exhaust gas line which consists of a solids-entraining reactor 4. The exhaust gas flowing in the solids-entraining reactor 4 has the ^following composition: 17 o• e o* I I TABLE I. GAS COMPOSITION IN THE SOLIDS-ENTRAINING

REACTOR

N

2 02

H

2 0

CO

2

CO

SO

2 HC1

HF

dust dibenzodioxins and dibenzofurans 26 7 6 4 0.1 100 50 <400 400 to 73 to 18 to 36 to 23 to 1% to 200 mg/sm 3 to 80 mg/sm 3 10 mg/sm 3 to 600 mg/sm 3 1 to 10 ng TE/sm 3 o• e e *r The solids-entraining reactor 4 fed from the supply bin 5 through the feed line 6 with 0.1 to 2 g/sm 3 exhaust gas of a pneumatically conveyed mixture of a solid adsorption agent AA consisting of 50 by weight bentonite and 50 by weight kaolinite so that the solid adsorption agent contacts exhaust gas flowing through the solids-entraining reactor 4. The mixed adsorbents 18 have a median particle diameter d 50 of 20 micrometers.

As a result of heat losses and effects of mixing the gas-solids suspension conducted in the solids-entraining reactor 4 assumes a temperature of about 140 0 C and at that temperature enters an electrostatic precipitator 7, which consists of three fields, with which respective dust bins or collection spaces 8a, 8b, 8c are associated. About 90 by weight of the dust and mixed adsorbents are collected in the dust bin 8a of the first field of the electrostatic precipitator 7. About 4 by weight of the dust and mixed adsorbents are collected in the dust bin 8b and about 1% in the dust bin 8c so that the purified gas leaving the electrostatic precipitator 7 contains 40 mg/sm 3 dust. In a steady-state equilibrium, 5 to 100 g of the mixed solids per sm 3 exhaust gas are recycled from the dust bin 8a to the solids-entraining reactor 4 so that the mixed adsorbents are contacted several times with the exhaust gas in the solids-entraining reactor. The collected solids SC in the collection spaces are supplied to the solidsentraining reactor 4 through the recycle line 9. The purified exhaust gas which leaves the electrostatic precipitator 7 through line 10 contains polyhalogenated 19 7 dibenzodioxins and dibenzofurans in a concentration 0.1 ng TE per sm 3 and is at a temperature of about 120 0 C. Before it is discharged into the atmosphere, the still existing gaseous pollutants, particularly CO,

SO

2 HCI, and HF, may be separated by following purification processes. The solids collected in the dust bins 8b and 8c are mainly enriched with the alkali salts and are discharged through line 11. A part of the solids from the dust bin 8a are removed from the system and recycled to the sintering plant 1 through line 12. The solids leaving the line 11 are deposited in a dump.

Also shown in the drawing a bag filter B can be connected downstream of the electrostatic precipitator 7 to further purify the purified gas from the electrostatic precipitator 7 by removing additional dust. Collected solid residues can also be returned from the bag filter B to the reactor 4 via a line connected to line 12. A cyclone R can be connected to receive the gas-solids suspension from the solids-entraining reactor 4 and to recover recovered solids for return to the reactor 4 via return line SL. The cyclone R delivers partially purified gas to the electrostatic precipitator 7 in the embodiment shown in the drawing.

The embodiment of the process for purification of exhaust gases from sintering processes enables capital investment, amounts of products and operating costs to be minimised and the embodiment produces products which may be dumped substantially without difficulty or which may be processed in the sintering process or may be recycled to the purification process after regeneration.

The embodiment preferably utilises inorganic materials as adsorbents as much as possible and minimises the use of activated carbon as an adsorbent so that risks involved in such use regarding operating safety of the absorption plants may be avoided as much as possible.

The embodiment of the purification process preferably meets new and more rigorous requirements regarding the purification efficiency and the economy of the process.

S 15 The embodiment of the purification process for exhaust gases from sintering processes ensures that low pollutant concentrations are maintained in the purified gas while maintaining process economy, even in case of fluctuations of concentrations of several pollutants, especially maintaining polyhalogenated dibenzodioxin and dibenzofuran concentration 0.1 ng TE per 20 sm3 (TE toxicity equivalent in accordance with the NATO standard).

In the exemplary embodiment, the entire exhaust gas from the sintering i conveyor is contacted above the dew point at a temperature from 90 to 1800C and at a velocity from 6 to 20 metres per second with a solid adsorption agent comprising clays, layer silicates, and diatomaceous earth or mixtures thereof within a gas-solids suspension for a reaction time from 0.5 to 10 seconds; dust and the other solids in the gas-solids suspension are subsequently jointly separated from the gas-solids suspension to form separated solids and part of the separated solids is again contacted with the exhaust gas from the sintering conveyor. The median particle diameter, d 50 of the solid adsorption agent is from 5 to 100 micrometres and the mean suspension density of the gas-solids suspension is from 5 to 500 g solids per sm 3 exhaust gas.

The process in accordance with the embodiment may be carried out to reliably provide a pure gas containing polyhalogenated dibenzodioxins and dibenzofurans in a concentration 0.1 ng TE per sm3 although the contaminated exhaust gas from the sintering process may contain polyhalogenated dibenzodioxins and dibenzofurans in an amount from 1 to ng TE per sm 3 Besides, the purified gas contains 50 ng/sm 3 polycyclic hydrocarbons and 150 ng/sm3 polyhalogenated hydrocarbons. The content of carbon in organic compounds in the purified gas is 10 mg sm 3 The gas velocity from 6 to 20 metres per second which is contemplated according to the embodiment is achieved by bringing dust-containing exhaust gas from the sintering conveyor into contact with the solid adsorption agent in a solidsentraining reactor. The clays are naturally occurring aluminosilicates having a layer silicate structure and different water contents. Diatomaceous earth (diatomate) is a fine-grained powder and consists of 70 to 90% amorphous silica, 3 to 12% water, and small amounts of organic components. The diatomaceous earth is normally fumed and is chemically inert and melts at 1200 to 17000C.

It is also contemplated in accordance with the embodiment to use 20 kaolinite, bentonite, illite or mixtures thereof as the clays. The clays have proved to be particularly satisfactory in the practice of the process because their use has the result that the pure gas reliably contains the pollutants in the abovementioned concentrations and, as a rule, in even lower concentrations, although the adsorption is effected in the presence of the dust, the water vapour, and the pollutants contained in the exhaust gas. Kaolinite has the composition A1 2 0 3 .2SiO 2 .2H 2 0 and the water is chemically bound and escapes only at temperatures from 390 to 4500C. The kaolinite has a layered structure.

Bentonite is a bleaching earth. Illite is a mica-like clay mineral having the composition Ko.

7 (Al 2 Mg 3 Fe 2 Fe 3

(OH)

2 (Si3.3 Alo.

7 It is also contemplated in accordance with the embodiment that 2 to by weight activated carbon may advantageously be mixed with the preferred clays, the layer silicates, the diatomaceous earth or the mixtures of the substances. That measure does not adversely affect the safety of the plant in operation and increases the adsorption capacity of the process. For the purpose of the embodiment it also may be desirable to add 10 to 40% by weight of a mixture of naturally occurring zeolites to the solid adsorption agent, i.e. to the clays, the layer silicates, the diatomaceous earth or the mixtures consisting of the substances. These mixed zeolites preferably consist of 10 to 20% by weight mordenite, 60 to 70% by weight clinoptilonite, 0 to 5% by weight :.montmorillonite, with the balance Si0 2 This embodiment of the process particularly ensures that the price of the adsorbent is low while the efficiency of the process is not adversely affected.

15 The apparatus for performing the process according to the embodiment consists of a solids-entraining reactor, a multifield electrostatic precipitator, and a solids recycle line, which connects the collecting space of the first field of the electrostatic precipitator or the collecting spaces of the first and second fields of the electrostatic precipitator to the exhaust gas line leading to or 20 advantageously comprising the solids-entraining reactor. The polycyclic and polyhalogenated hydrocarbons, preferably the polyhalogenated dibenzodioxins and dibenzofurans, and the dust-like solid particles, which are contained in the exhaust gas from sintering may be substantially completely separated by this apparatus so that the exhaust gas leaving the electrostatic precipitator contains 40 mg/sm 3 dust and contains polyhalogenated dibenzodioxins and dibenzofurans in concentrations 0.1 ng TE per sm 3 The gaseous pollutants contained in the exhaust gas, particularly CO, S02, HCI, and HF, may be removed from the exhaust gas stream in known manner by following purification processes.

R A

A''%L

In an additional embodiment or preferred feature of the invention the electrostatic precipitator may be connected to a downstream bag filter so that the additionally purified gas from the bag filter has a dust content which is significantly below 40 mg/sm 3 and peak dust content in the raw gas may be handled.

Alternatively, the apparatus may consists of a solids-entraining reactor, a bag filter having a collecting space and a solids recycle line which connects in collecting space of the bag filter to the exhaust gas line leading to or comprising the solids-entraining reactor. That apparatus may also be used to substantially completely separate the dust-like solid particles and the polyhalogenated dibenzodioxins and dibenzofurans so that the exhaust gas stream leaving the bag filter contains dust in a concentration 50 mg/sm 3 and polyhalogenated dibenzodioxins and dibenzofurans in a concentration 0.1 ng TE per sm3.

15 According to an embodiment the exhaust gas line conducting the exhaust gas from the sintering conveyor may consist of a solids-entraining reactor. This results in a simplification of the apparatus so that capital investment and S";operating costs are decreased.

Finally it is contemplated in other embodiments, a cyclone may be 20 provided between the solids-entraining reactor and the multifield electrostatic precipitator which communicates through a solids line with the solids-entraining reactor. The cyclone relieves the following process equipment and the recovered solids separated by the cyclone are recycled to the solids-entraining reactor.

SLi) The electrostatic precipitator 7 can be replaced by a bag filter in additional embodiments not shown in the drawing.

While the embodiment has been illustrated and described as embodied in a process and apparatus for purifying exhaust gases from a sintering process, it is not intended to be limited to the details shown, since various modifications and structural changes may be made !ewithout departing in any way from the spirit of the present invention.

oao Without further analysis, the foregoing will so fully reveal the gist of the present embodiment that others can, by applying current knowledge, readily adapt e, it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What is claimed is new and desired to be protected by Letters Patent is set forth in the appended claims.

21 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A process of separating polysyclic and polyhalogenated hydrocarbons from an exhaust gas of a sintering process, said exhaust gas containing dust and said process including the steps of bringing the entire exhaust gas from the sintering process into contact with a solid adsorption agent selected from the group consisting of clays, layer silicates, diatomaceous earth and mixtures thereof within a gas-solids suspension for a reaction time of from 0.5 to seconds above a dew point of the exhaust gas at a temperature from 90 to 1800C and at a velocity from 6 to 20 metres per second; subsequently separating said solid adsorption agent and said dust jointly from the gas-solids i: suspension to form separated solids and contacting said exhaust gas from the sintering process with a part of the separated solids; wherein said solid adsorption agent has a median particle diameter, d 5 0 of from 5 to 100 micrometers and the gas-solids suspension has a mean suspension density of from 5 to 500 g solids per sm 3 of said exhaust gas.

2. The process as defined in claim 1, wherein said clays include kaolinite, bentonite, illite and mixtures thereof.

3. The process as defined in claim 1, further including admixing from 2 to by weight of activated carbon with said solid adsorption agent prior to the bringing of the exhaust gas into contact with the solid adsorption agent.

4. The process as defined in claim 1, further including admixing from 10 to by weight of a mixture of naturally occurring zeolites the clays with said solid adsorption agent prior to the bringing of the exhaust gas into contact with the solid adsorption agent.

The process as defined in claim 4, wherein said zeolites consist of 10 to by weight mordenite, 60 to 70% by weight clinoptilonite, 0 to 5% by weight montmorillonite, with a balance consisting of Si0 2

Claims (11)

1. 6. The process as defined in claim 1, wherein said polycyclic and polyhalogenated hydrocarbons include polyhalogenated dibenzodioxins and dibenzofurans.
2. 7. The process as defined in claim 1, wherein said sintering process is a process of sintering iron ore performed in a sintering apparatus having a sintering conveyor.
3. 8. An apparatus for performing the process according to any one of claims 1 to 7 wherein the apparatus includes: means for bringing the entire exhaust gas from the sintering process into ,i.i contact with a solid adsorption agent within a flowing gas-solids suspension, wherein said means for bringing said entire exhaust gas into contact with the solid adsorption agent includes a solids-entraining reactor means for subsequently separating said solid adsorption agent and said dust jointly from the gas-solids suspension to form separated solids, wherein S. ~said means for subsequently separating includes a multifield electrostatic precipitator having at least a first and second collecting space (8a, 8b) in respective first and second fields thereof; and means for bringing said exhaust gas from the sintering process into contact with a part of the separated solids including a solids recycle line (9) connecting at least one of said collecting spaces (8a, 8b) with an exhaust gas line conducting said exhaust gas from said sintering process.
4. 9. The apparatus as defined in claim 8, wherein said exhaust gas line consists of said solids-entraining reactor The apparatus as defined in claim 8, wherein said exhaust gas line is connected to said solids-entraining reactor 24
5. 11. The apparatus as defined in claim 8, further including a bag filter for further purification of a purified gas issuing from said electrostatic precipitator said bag filter being connected downstream of said electrostatic precipitator
6. 12. The apparatus as defined in claim 8, further including a cyclone for recovering recovered solids from the gas-solids suspension, wherein said cyclone is connected to the multifield electrostatic precipitator and is connected to the solids-entraining reactor so as to receive the gas-solids suspension issuing from the solids-entraining reactor and is also connected to the solids-entraining reactor by a solids line for delivery of the recovered solids from the gas-solids suspension thereto.
7. 13. An apparatus for performing the process according to any one of claims 1 o: to 7 wherein the apparatus includes: :o means for bringing the entire exhaust gas from the sintering process into contact with a solid adsorption agent within a flowing gas-solids suspension, wherein said means for bringing said entire exhaust gas into contact with the solid adsorption agent includes a solids-entraining reactor means for subsequently separating said solid adsorption agent and said dust jointly from the gas-solids suspension to form separated solids, wherein i: said means for subsequently separating includes a bag filter having a collecting space; and means for bringing said exhaust gas from the sintering process into contact with a part of the separated solids including a solids recycle line (9) connecting said collecting space of the bag filter with an exhaust gas line conducting said exhaust gas from said sintering process.
8. 14. The apparatus as defined in claim 13, wherein said exhaust gas line consists of said solids-entraining reactor The apparatus as defined in claim 13, wherein said exhaust gas line is connected to said solids-entraining reactor
9. 16. The apparatus as defined in claim 13, further including a cyclone for recovering recovered solids from the gas-solids suspension, wherein said cyclone is connected to the bag filter and is connected to the solids- entraining reactor so as to receive the gas-solids suspension issuing from the solids-entraining reactor and is also connected to the solids-entraining reactor by a solids line for delivery of the recovered solids from the gas- solids suspension thereto.
10. 17. A process of separating polysyclic and polyhalogenated hydrocarbons from an exhaust gas of a sintering process, said exhaust gas containing dust and said process, the process substantially as hereinbefore described and illustrated with reference to the accompanying drawing.
11. 18. An apparatus for performing the process according to any one of claims 1 to 7, the apparatus substantially as hereinbefore described and illustrated with reference to the accompanying drawing. S DATED this 27th day of May 1999 METALLGESELLSCHAFT AKTIENGESELLSCHAFT I *WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP:RJS:VRH DOC 27 AU4025695.WPC -o ABSTRACT OF THE DISCLOSURE The process for separating toxic organic substances from a dust-containing exhaust gas from a sintering process, particularly a process of sintering iron ore,includes bringing the entire exhaust gas from a sintering conveyor into contact with clays, layer silicate, and diatomaceous earth or mixtures thereof within a gas-solids suspension for a reaction time of from 0.5 to 10 seconds above the dew point at a temperature from 90 to 180°C and at a velocity from 6 to 200 meters per second. The median particle diameter, d 5 0 of the solid adsorption agent in the gas-solids suspension is from 5 to 100 micrometers and the mean suspension density of the gas-solids suspension is from to 500 g solids per sm 3 exhaust gas. The dust and other solids are subsequently jointly separated from the gas-solids suspension, and part of the separated solids is again contacted with the exhaust gas from the sintering conveyor. An apparatus for carrying out the process is also described. 26