APPARATUS AND METHOD FOR PRODUCING DREST IRON-ORE BRIQUETTE AND/OR PELLET FROM STEEL MAKING CONVERTER FLUE-DUST, CONVERTER SLUDGE OR RED MUD

This invention relates to an apparatus and method for achieving ecologically pure, non- emissive production of drest iron-ore briquette and/or pellet from steel making converter flue- dust, converter sludge or red mud.

During making steel by means of steel making converter a huge amount of flue-dust (filter dust) is created requiring a need of by pass, filtering and deposing. Flue-dust is a harmful waste category by-product of steel making, deposing and elimination of which cause a very serious problem. Making 100 tons of steel 1 ton of flue-dust is arisen filtered in the flue-gas system from the flue-gas. Flue-dust created for production of carbon steels contains no little amounts of ferrous oxides, heavy metals, first of all zinc and lead, and its approximate composition varies according to ways of production and steel types to be produced, indeed. The most significant components of the flue-dust are iron and zinc, but its lead content is also not negligible.

A huge amount of flue-dust of steel making converter steel and electrosteel as a by- product of steel making had been being collected during decades, and although several, mainly pyrometallurgical solutions had been proposed to exploit it, its recycling and elimination is not yet solved, since high energy requirement of known solutions makes the reuse of flue-dusts having lower Zn and Pb content economically unfavourable and in addition, these methods are as contaminating environmentally as the iron and steel production in itself. Nevertheless, among above solutions the Waelz process is worthy of mention, the principal products of which are ZnO also known as Waelz-oxide, and a mixture of metal iron and slag, from the fraction of smaller size granules of which an agglomerate is produced and then batched into blast furnace along with the fractions of greater size granules.

Such a method is disclosed in the patent document EP 0007662 using the Waelz process with a base material containing zinc- and iron-oxide - e.g. flue-dust - batched into a sloped pipe furnace along with reductive aids containing solid coal and comburent materials and blowing in by oxygen in order to rise its temperature to 800 ⁰ C. Zinc-oxide created during Waelz process is filtered as a coarse powder to be used in zinc smelters. Common drawback of similar reductive pyrometallurgical processes developed for processing flue-dusts and sludges is the high temperature used (Fastmet 1300 ⁰ C, Fastmelt 1000 ⁰ C, ITmk3 process 1400 ⁰ C, Primus HOO ⁰ C, Oxifines 1300°C, Contop 2000°C, Plasma furnace working 5000°C, Scandust 3000°C, vacuum treatment process 800°C), consequently the energy consumption is also high, therefore the main scope of these processes is to yield more valuable metals as Zn, and the recovery ferrous metals remains unsolved and further waste materials arise. Consequently, such methods are adapted to process flue-dust created during electro steel production only. A further disadvantage is the fact that ZnO, the most valuable product, is frequently contaminated by lead. Patent document JP 57057842 discloses a method to recover Zn and Fe from converter flue-dust, comprising mixing flue-dust and sludge coming from a metallurgical plant with 5-30 % of powdered burnt lime, granulating the mixture to obtain a granule size of 5-70 mm, then using this granulate for cooling overheated steel batch of a converter, thus the Fe content of the granulate dissolves in the melt, CaO regulates basicity of the slag, Zn and other metals evaporate and cooling outside the converter may be collected in dust filters. With this method both Zn and Fe can expediently be recovered, putting the lost heat of the converter to account. However, it is a drawback that this method cannot be used as a separate process apart from steel making, and that ZnO obtained is largely contaminated by lead and other heavy metals.

Working out solutions relating to process flue-dusts and sludges containing Fe and heavy metals shifted to hydrometallurgy due to pyrometallurgical processes being expensive. In a variant of EZINEX process adaptable in processing flue-dust having high Fe content the flue-dust is mixed in an autoclave containing ammonium-chloride solution, resulting in dissolution of Zn and contaminants, the insoluble components are filtered and injected into iron melt in an induction furnace, where the Zn remained evaporates and is turned back to the autoclave, while the Fe content will be recovered by the iron melt. Adding powdered zinc to the solution mixed in the autoclave, the contaminants having lower electronegativity than the Zn, mainly Cu and Pb, can be removed by means of a filter. Solution containing Zn(NH) ₃ CI ₂ cleaned this way can be electrolyzed in order to obtain metal Zn. The drawback of this method is that it becomes cost effective only in case of inserting an induction furnace into the process when processing flue-dust and sludges having high Fe content, resulting in higher energy consumption, that is flue-dust and sludges having high Fe content cannot be processed economically by this method. A similar method is discussed by the published application EP1878806, which is cheaper but it is adaptable to process flue-dusts of arc-furnace having high Zn content only. The main objective of all above solutions is - Z -

to recover Zn content of flue-dusts and sludges created during steel making operation, thus the

Fe-oxides occurred in a very large amount may not be recovered in a sufficient extent.

The third kind of metallurgical waste material accumulated in a very huge amount is the red mud a by-product of alumina production. Namely 0,5-1,5 tons of red mud arise by production of 1 ton of Al, the NaOH content of which is very high making this waste very hazardous environmentally. Fe content of the red mud is also very high, therefore, the pollution can be eliminated and its Fe content can be recovered by providing a method economically acceptable. Published patent document CN 101204681 discloses a method to process red mud comprising the steps of separating Fe-oxides by electromagnetic field, wetting, sieving and then baking the crude ore in a magnetic baking furnace. Repeating these steps iron-ore sinter of 55-65

% purity is finally obtained. A drawback of this method is that a large amount of dead material containing sodium-aluminium-silicate arises, use of which is unsolved.

Therefore, the object of the present invention is to provide an apparatus and a method for recovering metal content, mainly Fe-content of steel making converter flue-dust, converter sludge and red mud, eliminating above drawbacks of prior art solutions, that is to decrease specific costs of production, to ameliorate the purity of products and to minimize or eliminate the amount of wastes created by the process, as well as to be able to produce cheap secondary products as iron ore briquettes/pellets.

The object of the present invention is achieved by providing an apparatus for producing drest iron-ore briquette from steel making converter flue-dust, converter sludge or red mud, comprising converter flue-dust storing container, reagent container, autoclave, buffer vessel arrangement, separator, dryer unit, buffer vessel, evaporator, water cooler, driving water vessel and separator unit, and the apparatus is further provided by a mixing unit with pouring slot and a briquetting unit consisting of an endless casting mould belt stretched between two drums, at least one of which is driven, and open casting moulds with closed bottom and cavity walls made of elastic material are arranged in at least one row on the endless casting mould belt, and the pouring slot is provided above the endless casting mould belt.

Preferably each bottom and cavity walls of said casting moulds are arranged beneath the surface of the endless casting mould belt. Each bottom and cavity walls of said casting moulds are shaped with a moulding slant having a range between 0° and 10°, preferably within a range of 1° and 6°, and more preferably it is 4° in relation to the normal of the endless casting mould belt. A releasing-cone is shaped in the casting mould, preferably in the middle thereof, starting from the bottom and protruding at most up to the surface plane of the endless casting mould belt.

The releasing-cone is advantageously shaped as a truncated cone, and moulding slant of its generatrices is between 0° and 10°, preferably within a range of 1° and 6°, and more preferably it is 4°.

The cavity walls of open casting mould shaped integrally with said endless casting mould belt are made of elastic material, preferably gum or silicone.

The elastic casting mould is in a compressed state while it is between the skirt of the drum and the endless casting mould belt.

The separator comprises a centrifugal separator or a wash box.

According to another aspect of the present invention a method is provided for producing drest iron-ore briquette from steel making converter flue-dust and/or converter sludge, comprising the step of: - adding base material from a storing container containing converter flue-dust and/or converter sludge into an autoclave having internal mixing device and heating device , and adding water from a driving water vessel and reagent into said autoclave containing said base material , then continuously mixing said solution thus obtained in the autoclave by means of the mixing device , while maintaining its temperature on a permanent value by means of the heating device , and elevating the temperature of the solution to a range between 55-85 ⁰ C and adding 2 mass%-30 mass% reagent to the base material in the autoclave , while mixing it permanently, thus transforming the heavy metal (Me) content of the flue-dust into Me-chloride and Me-ferrite or

Me-salt in the one hand, and transforming its Fe-oxide content into solid colloid phase in the other hand, diverting the mixture into a wash box or separator, and separating the solid phase containing Fe-oxide and Me-chloride phase, then conveying the solid phase containing Fe-oxide into a mixing unit from the separator, adding additive material containing CaO, and mixing this mixture into a pasty state as being iron-ore pulp, then pouring the latter into open casting moulds with closed bottom and cavity walls made of elastic material arranged in an endless casting mould belt stretched between two drums, evening the surface while moving steadily said endless casting mould belt between the two drums, and allowing the iron-ore pulp to set as solid iron-ore briquette , and compressing said casting moulds made of elastic material between the casting mould belt and the drum, thus releasing the solid iron-ore briquette from the casting mould. Said reagent comprises ammonium-salt, preferably crystalline ammonium-chloride (NH ₄ CI).

Said reagent is added in an amount of 2-10 mass% in relation to the mass of base material

Ammonium-chloride (NH ₄ CI) is added in an amount of 4-8 mass%.

Ammonium-chloride (NH ₄ CI) is added in an amount of 6 mass%. Said reagent comprises a weak acid, preferably acetic acid (CH ₃ COOH). A weak acid, preferably acetic acid (CH ₃ COOH) is added in an amount of 10-30 mass% in relation to the mass of base material. A weak acid, preferably acetic acid (CH ₃ COOH) is added in an amount of 15-25 mass% in relation to the mass of base material.

A weak acid, preferably acetic acid (CH ₃ COOH) is added in an amount of 20 mass% in relation to the mass of base material.

The temperature of the autoclave is elevated to a range between 65-80 ⁰ C. The temperature of the autoclave is elevated to a range between 75-80 °C.

The temperature of the autoclave is elevated to a range between 70-75 ^β C. The temperature of the autoclave is elevated to a range between 65-70 ⁰ C. Overall ZnCI ₂ and PbCI ₄ content of the Me-chloride product is at least 90 mass%. The heavy metal (Me) content of the flue-dust is transformed into Me-chloride in 1,5 hours.

Me-ferrite having a zinc-ferrite (ZnFe2O4) content of at most 90 mass% forming a solid colloid phase with Fe-oxides is obtained.

Fe-oxide-Me-ferrite solid phase is forwarded to a dryer unit.

Overall Pb-acetate (Pb(C ₂ H ₃ O ₂ J ₂ ) and Zn-acetate (C ₄ Hi ₀ O ₆ Zn) content of the Me-acetate product is at least 90 mass%, and they are separated in a separator from each other. Additive material containing CaO comprises hydrated lime and/or burnt lime. Additive material containing CaO comprises cement.

The Fe content of the briquette is at least 50 mass%, and it is provided with a through bore having a shape according to the releasing-cone. According to ma further aspect of the invention a method is provided for producing drest iron-ore briquette from red mud, comprising the step of: adding base material from a storing container containing red mud into an autoclave having internal mixing device and heating device , and adding reagent into said autoclave containing said base material , then continuously mixing said mixture in the autoclave , while maintaining its temperature on a permanent value, adjusting the temperature of the mixture to a range between

55-85 °C and adding ammonium-chloride reagent to the base material in the autoclave, while mixing it permanently, and reducing Fe-chloride residual thus created into Fe-oxide by means of ammonia, diverting the mixture into a wash box or a separator , and separating the solid phase containing Fe-oxide and residuals containing NaOH and AI ₂ O ₃ of the mixture, and creating zeolite and water by adding 20-25 mass% of water glass (Na ₂ SiO ₃ ) to the solute residuals containing

NaOH and AI ₂ O ₃ , and then conveying the solid phase containing Fe-oxide into a mixing unit from the separator , adding additive material containing CaO, and mixing this mixture into a pasty state as being iron-ore pulp, then pouring the latter into open casting moulds with closed bottom and cavity walls made of elastic material arranged in an endless casting mould belt stretched between two drums, evening the surface while moving steadily said endless casting mould belt between the two drums, and allowing the iron-ore pulp to set as solid iron-ore briquette , and compressing said casting moulds made of elastic material between the casting mould belt and the drum, thus releasing the solid iron-ore briquette from the casting mould.

Ammonium-chloride (NH ₄ CI) is added in an amount of at most 15-25 mass% in relation to the mass of base material .

Ammonium-chloride (NH ₄ CI) is added in an amount of 20 mass%. The temperature of the autoclave is elevated to a range between 70-80 ⁰ C. Solid phase containing Fe-oxide is forwarded from the separator to a dryer unit and then to a mixer.

Additive material containing CaO comprises hydrated lime and/or burnt lime. Additive material containing CaO comprises cement.

The invention will be disclosed in details by its advantageous embodiments referring to the drawing attached. In the drawing:

Fig. 1. shows the dressing a briquetting apparatus according to the invention,

Fig. 2. briquetting unit of the apparatus according to the invention is shown,

Fig. 3. a cross-sectional view of the casting mould arranged on the casting belt, and Fig. 4. axonometric view of a piece of briquette according to the invention.

Fig. 1. depicts schematically the apparatus according to the invention. In this embodiment the apparatus comprises at least one converter flue-dust storing container 1, four reagent containers 2, an autoclave 4, a buffer vessel arrangement 6, a ^' centrifugal separator 7, a dryer unit 8, a mixing unit 9, a pouring slot 10 connected directly - or in this embodiment, by means of an intermediate charging tank 10a - to the mixing unit 9, a casting mould belt 11, a buffer vessel 5, an evaporator 12, a water cooler 13, a driving water vessel 3, and a separator unit 14 (or wash box).

Converter flue-dust (filter dust) and/or sludge from steel making converter or red mud as the base material A of the methods according to the invention is bulked respectively in a flue-dust storing container 1. Autoclave 4 is a well known device in the art provided by internal mixing element K and an internal or external heating unit F adapted to heat the solution to be processed. Buffer vessel arrangement 6 comprises at least one storing vessel - eight vessels in the drawing - being suitable to procedurally store sludge having high Fe-content obtained in the autoclave 4. Centrifugal separator 7 is a centrifugal device preferably adapted for reducing water content of the sludge stored in the buffer vessel arrangement 6 and also for washing and separating its Fe, heavy metal and reagent content, which might be replaced by a rotary filter or a settling tank. Dryer unit 8 is a device adapted to further reduce moisture content of sludge residues exiting the separator 7 (or settled in a settling tank) with low water content and high FeO concentration, e.g. a gas-fired or electric drying furnace well known in the art. Mixing unit 9 is a batch mixer like device preferably with fixed vertical axis, adapted for precisely adjusting and adding, according to the present invention, the water content necessary for briquetting of highly FeO concentrated solid phase. In this embodiment mixing unit 9 is a drum mixer, and the charging tank 10a having a casting mould 10 is adapted for collecting and forwarding to the briquetting machine the iron-ore pulp prepared in this mixer. Charging tank 10a might be omitted, and in this case the casting mould 10 is arranged in the mixing unit 9 as an output opening thereof. In this description the term "briquette" or "iron-ore briquette" means iron-ore briquette or pellet differing in size only.

Briquetting unit shown in Fig. 2. consists of an endless casting mould belt 11 formed like a known conveyor belt: a belt S is stretched between two drums Dl, D2, at least one of which is driven (drive not shown in the drawing). Open casting moulds 11a in one or more rows shown in details in Fig. 3. are formed on the endless casting mould belt 11. As it can be shown in the drawing, each casting mould 11a arranged beneath the surface of the endless casting mould belt 11 is open above with closed bottom, bottom and cavity walls Hf of said casting moulds Ha are shaped with a moulding slant (α) having a range between 0° and 10°, preferably within a range of 1° and 6°, and more preferably it is 4" in relation to the normal of the endless casting mould belt 11. A releasing-cone Hk is shaped in the casting mould Ha, preferably in the middle thereof, starting from the bottom and protruding at most up to the surface plane of the endless casting mould belt H. The releasing-cone Hk is shaped as a truncated cone, and moulding slant (α) of its generatrices is equal or similar than that of the cavity walls Hf, namely it is between 0" and 10°, preferably within a range of 1° and 6°, and more preferably it is 4°. Endless casting mould belt 11 and cavity walls Hf of open casting moulds Ha shaped integrally with said endless casting mould belt (11) are made of elastic material, preferably gum or silicone. This solution advantageously allows deformation of the casting moulds Ha because of the belt tensioning, that is casting moulds Ha will be compressed between the skirt of the drum Dl, D2 and the endless casting mould belt 11 resulting in releasing, detruding by rights, of the solidified iron-ore briquette P from the casting moulds Ha, and falling into e.g. a container T. The empty casting mould Ha recover its original shape by its elasticity and/or during recharging.

Turning back to the Fig 1., the buffer vessel 5 arrangement shown is adapted to store a solution of reagents and heavy metal compounds evacuated from autoclave 4. The moisture content of the solution stored in buffer vessel 5 is eliminated by means of an evaporator 12, evaporating alkali and water are drained back to the driving water vessel 3 through a water cooler 13.

Cemented crystalline evaporation residue mostly containing Zn and Pb remained in evaporator 12 is separated by gravity separation, particularly by flotation, in a separator unit 14 into Pb containing heavy cement and Zn-chloride.

Process according to the present invention is achieved by above described apparatus according to the invention. The method followable also in Fig. 1., comprises the first step of adding base material A from the container 1 storing flue-dust and/or converter sludge into the autoclave 4. The mean grain size of the solid particles of base material A is between 0 and 5 mm, preferably 0 and 1,5 mm. Base material A may comprise flue-dust in itself as well as flue-dust or converter sludge, flue-dust and converter sludge, or red mud alone, an approximate composition of which is shown in the Table 1.

TABLE 1.

As it was mentioned above, flue-dusts created particularly for production of carbon steels contains no little amounts of ferrous oxides, heavy metals, first of all zinc and lead, and its approximate composition varies according to ways of production and steel types to be produced, within the ranges denoted approximately. In the next step of the method according to a preferred embodiment of the invention ammonium salt, preferably crystalline ammonium-chloride (NH ₄ CI) and, if flue-dust is to be processed alone, water from the driving water vessel 3 is added by adequate amount to the base material A charged in the autoclave 4 provided by internal mixing element K and a heating unit F adapted to heat the solution. Adding water is not absolutely necessary in case of converter sludge processing, because of its water content, but adding water might serve for adjusting dilution. Flue-dust processing needs adding of said (NH ₄ CI) reagent in an amount of 2-10 mass%, preferably in an amount of 4-8 mass%, more preferably in an amount of 6 mass%, in relation to the mass of base material A.

Subsequently, while mixing the solution produced according to above in the autoclave 4, its temperature is elevated to a range between 55-85 "C, preferably between 60-75 "C, and more preferably between 65-70 ⁰ C, by means of the heating unit F. We have found during tests conducted by us, that an oversaturated solution is obtained at the preferred temperature of the process and by permanent mixing, so that the solid fractions precipitate relatively rapidly accelerating the process and reducing the necessary level of temperature at once, thus allowing energy saving.

While mixing continuously in the autoclave, the heavy metal Me content of the flue-dust, mainly Zn (Ni, Co, Cd, Cu etc. in less quantity, because of their less proportion):

ZnO+2NH ₄ CI => ZnCI ₂ +NH ₃ +OH, and its Pb content dissolves:

PbCI ₂ +(NH ₄ )CI => (NH ₄ ) ₂ PbCI ₄ , in one hour, approximately. With this reaction alkali salt solution (NaOH) as well as Zn- ferrite (ZnFe ₂ O ₄ ) are also produced, the latter forms with ferrous-oxides a solid colloid phase in the mixture.

After these reactions have been completed, the relatively homogenous and suspension like solution is conducted to a settler device, preferably to a - e.g. centrifugal -separator 7. In the separator 7 the Fe-oxide-Zn-ferrite phase will be separated from the alkali-salt solution (NaOH) containing Zn-chloride and cemented lead-solution. The latter is filtered, then forwarded to the evaporator 12, while Fe-oxide-Zn-ferrite solid phase is batched into the dryer unit 8, if necessary, where it loses the main portion of its moisture content yet remained. Nevertheless, the drying process might be omitted, if the actual moisture content of the Fe-oxide-Zn-ferrite phase meets the moisture content required to further processing.

Alkali-salt solution (NaOH) containing Zn-chloride and cemented lead-solution is boiled off in the evaporator 12, and evaporated NaOH and steam mixture redirected into the driving water vessel 3 through the water cooler 13, and it may be recycled feeding the autoclave 4. Material concentrated in evaporator 12, which substantially is a mixture of Zn-chloride and cemented lead, is forwarded to the gravity separator unit 14 in order to separate Zn-chloride and cemented lead by means of a flotation process. Flotation process is achieved in a viscous medium, e.g. in oil or glycerine. Crystalline Zn-chloride is filtered out from the glycerine (e.g.), while the cement containing lead settles on the bottom of the gravity separator 14 thus it can be easily removed therefrom. Crystalline Zn-chloride thus obtained might be used e.g. as a base material in the pharmaceutical industry, or metal zinc can be produced from it by electrolysis, and the cemented lead is adapted to be further processed to obtain heavy cement.

After being dried (or without drying) the Fe-oxide-Zn-ferrite solid phase (a concentrate having an Fe-oxide content of at least 90 %) is forwarded by batches to the mixing unit 9, and admixing it with calcium hydrate or an additive containing CaO, e.g. cement, and mixing this mixture to achieve a pasty state. The amount of additive containing CaO is determined by requirements relating to the heat stability of iron-ore briquette to be produced.

In the next step of the method according to the invention the pasty iron-ore pulp homogenized in the mixer by the additive containing CaO is poured into open casting moulds 11a formed on the casting mould belt 11 through the pouring slot 10 of the mixing unit 9. In a preferred embodiment of the method according to the invention, when operating the mixing unit 9 intermittently, a pouring vat 10a can be located between the mixing unit 9 and casting mould belt 11, and said pouring slot 10 is formed on the vat 10a in this case. Casting mould belt 11 being moved continuously in the direction designated by arrow N in Fig. 2. away from pouring slot 10, the iron-ore pulp poured into the casting moulds 11a from the pouring slot 10 will be set as iron- ore briquettes P. The casting mould belt 11 is made of elastic material, preferably gum or silicone, thus each casting mould 11a turning on the drum Dl, D2 is compressed between the casting mould belt 11 and the drum Dl, D2 because of the belt tension, and the solid iron-ore briquette P is released from the casting mould 11a. Briquettes P can be collected in a container T placed at the end of the casting mould belt 11. Fig. 4. shows the briquette P according to the invention, the Fe content of which is at least 50 % and it is provided with a cavity according to the shape of the releasing-cone Ilk.

In a further embodiment of the method of the present invention the reagent NH ₄ CI can be replaced by a weak acid, e.g. acetic acid. In this case, the base material A is added from the container 1 storing flue-dust into the autoclave 4. Properties of the base material A are the same as described in the first embodiment above.

In the next step of the method according to a preferred embodiment of the invention acetic acid and, if flue-dust is to be processed alone, water from the driving water vessel 3 is added by adequate amount to the base material A charged in the autoclave 4 provided by internal mixing element K and heating unit F adapted to heat the solution. Converter sludge processing needs adding of acetic acid (CH ₃ COOH) reagent in an amount of 10-30 mass%, preferably in an amount of 15-25 mass%, more preferably in an amount of 20 mass%, in relation to the mass of base material A. Subsequently, while mixing the solution produced according to above in the autociave 4 by the mixing element K, its temperature is elevated to a range being between 70-80 °C, preferably between 75-85 °C, by means of the heating unit F. Mixing the solution continuously, lead-acetate (Pb(C ₂ H ₃ O ₂ J ₂ ), zinc-acetate (C ₄ H ₁₀ O ₆ Zn) and iron-oxide phases will be produced in the autoclave 4 in an hour approximately. In the issue, the product might be processed according to the first embodiment.

By means of the apparatus and method according to the present invention it is possible to produce iron-ore briquette from red mud, too. In this case red mud containing 40-50 mass% iron-oxide, 10 mass% NaOH and 15-18 mass% AI ₂ O ₃ alumina is processed in the apparatus according to the invention, such that adding to the red mud in the autoclave 4 at most 25 mass% ammonium-chloride, then further adding water glass (Na ₂ SiO ₃ ) to the waste liquor forming solute residues. In this case:

Na ₂ SiO ₃ + 2NaOH + 2AI ₂ O ₃ => 2Na ₂ OAI ₂ SiO ₇ .nH ₂ O zeolite is formed and iron-chloride remains as a residual, which can be transformed into ammonium-chloride and a solid phase containing at least 50 mass% of iron-oxide, if being treated by the ammonia produced. Iron-oxide may be processed into iron-ore briquette by the method according to the invention, preferably in a way according to the example 3. Zeolite might be used particularly in the production of detergents, reducing the phosphate content of which, and further can be exploited as a filler material for plastics, but it can be used in ion exchangers or as a litter material for pets - because of its absorbent property. The method according to the invention will further be disclosed by way of examples.

Example 1.

Flue-dust having a grain size of 0-1,5 mm and a zinc content of 25 mass% and lead content of 5 mass% has been forwarded to the storing container 1 by means of a pneumatic duct system provided by a compressor, and further into the autoclave 4 by a screw conveyor. Ammonium-chloride has also been added into the autoclave 4 by means of a screw conveyor. Water needed to dissolution has been added from the driving water vessel 3. 60 kg ammonium- chloride was added to every 1 ton of the flue-dust, and the temperature of this mixture has been maintained on 65 - 70 ⁰ C for one hour, while mixing it within the autoclave 4. During one hour, 260 - 300 kg zinc-chloride, 50 -60 kg cemented lead, approximately 50 kg alkali-salt solution and 700 - 800 kg iron-oxide solid phase containing also zinc-ferrite has been created. The solution was strained and then pumped into the evaporator 12; balanced and wet solid phase iron-oxide concentrate has been forwarded into the mixing unit 9 and mixed up to a pasty state with hydrated lime, then was poured onto the casting mould belt 11 with open casting moulds 11a having required shape and made of silicone, the mixture was evened above the moulds 11a, then left to set. At the end of the casting mould belt 11 the iron-ore briquettes thus obtained have been collected in a container.

Example 2. Converter sludge having a grain size of 0-1,5 mm and a zinc content of 4-5 mass% and lead content of 1-2 mass% has been forwarded to the storing container 1 by means of a slurry- pump. This sludge and concentrated technological acetic acid with a ratio of 1/0,2 have been pumped into the autoclave 4 in a closed system. After mixing it for one hour and at 80 ⁰ C iron- oxides has been produced in solid phase, while zinc and lead were produced in a solution of acetates. Further steps have similarly been achieved as in the first example. Example 3.

25 mass% of ammonium-chloride was added to a red mud batch having an iron-oxide content of 45 mass%, NaOH content of 10 mass% and containing AI ₂ O ₃ alumina as the balance in the autoclave 4. The temperature of this mixture has been maintained on 65 - 70 °C for one hour, while mixed it within the autoclave 4. Mixing and heating resulted in production of iron(ll)chloride and iron(lll)chloride deposits as a consequence of reduction of iron-oxides by the chlorohydric acid created from the ammonium-chloride, while ammonia was delivered. 20 mass% of water glass (Na ₂ SiO ₃ ) has been added to the remained waste liquor forming a solution containing NaOH and AI ₂ O ₃ . Thus zeolite and water have been produced from the waste liquor and settled a deposit comprising iron(ll)chloride and iron(lll)chloride. Zeolite and water were separated from the mixture, and the deposit comprising iron-chlorides was treated by the ammonia created in the reaction. Ammonia has oxidized the iron-chlorides, thus ammonium-chloride and iron-oxide were created. Solid phase iron-oxide concentrate has been forwarded to the mixer unit 9 and it was mixed with hydrated lime till became pasty, then was poured onto the casting mould belt 11 with open casting moulds 11a having required size and made of silicone. The mixture was evened above the moulds 11a, then left to set. The iron-ore briquettes P thus obtained have been collected in a container at the end of the belt 11.

Therefore, the main advantage of the apparatus and a method according to the present invention in comparison with the prior art apparatuses and a methods is that with recovering metal content, mainly Fe-content of steel making converter flue-dust, converter sludge and red mud the above drawbacks of prior art solutions are eliminated, that is the specific costs of production are decreased, the purity of products is ameliorated, and the amount of wastes created by the process are minimized or eliminated, as well as cheap secondary products as iron ore briquettes/pellets are obtained.