AU2021337156A1

AU2021337156A1 - Recirculating valuable substances from exhaust gas cleaning

Info

Publication number: AU2021337156A1
Application number: AU2021337156A
Authority: AU
Inventors: Alexander Fleischanderl; Martin Goetz; Robert Neuhold; Tobias Plattner
Original assignee: Primetals Technologies Austria GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 2020-09-01
Filing date: 2021-08-25
Publication date: 2023-03-02
Also published as: JP2023539667A; EP4208282A1; KR20230061432A; FI4208282T3; WO2022048965A1; EP3960279A1; EP4208282B1

Abstract

The application relates to a method and a device for recirculating valuable substances in a solid precipitate of an exhaust gas cleaning process for exhaust gas of the metallurgical industry, wherein, after at least a portion of the solid precipitate has been cleaned with dissolving water, extensive separation of water-insoluble material is carried out. The aqueous starting solution obtained during the separation is subjected to a plurality of successive treatment steps until, for a product solution obtained after the treatment steps have been passed through, a limit value specification is achieved. At least a portion of the water-insoluble material obtained during the separation, and/or of a solid material obtained during the treatment steps, and/or of a solid material contained from one or more products of one or more of the treatment steps, is fed to a primary process of the metallurgical industry. The device for recirculating valuable materials comprises appropriate devices such as a feeding device.

Description

Title of the invention

Recirculating valuable substances from exhaust gas cleaning

Field of industry

The invention relates to a method and to an apparatus for recirculation of materials of value in solid deposition products from an adsorptive and sodium bicarbonate-based offgas cleaning operation applied to offgas from a first primary process in metallurgical industry including deposition of a solid deposition product.

State of the art

Known adsorptive and sodium bicarbonate-based offgas cleaning methods including deposition of a solid deposition product give rise to large amounts of solid deposition products containing materials of value. The deposition products are often disposed of as hazardous waste.

Summary of the invention

Technical problem It is an object of the present invention to provide a method and an apparatus for recirculation of materials of value in solid deposition products.

Technical solution

This object is achieved by a method of recirculating materials of value in solid deposition product of an adsorptive and sodium bicarbonate-based offgas cleaning operation applied to offgas from a first primary process in the metallurgical industry including deposition of a solid deposition product, wherein combination of at least a portion of the solid deposition product with dissolution water results in substantial removal of water-insoluble material, which is characterized in that it comprises subjecting the aqueous starting solution obtained in the removal to multiple successive treatment steps until a limit specification is attained for a product solution obtained after implementation of the treatment steps, wherein one or more limit-relevant parameters are monitored and the treatment steps are controlled on the basis of the monitoring results, and wherein at least a portion - of the water-insoluble material obtained in the removal, and/or - of a solid material obtained in the treatment steps, and/or - of a solid material present from one or more products from one or more of the treatment steps is fed to the first primary process and/or to another primary process in the metallurgical industry.

Advantageous effects of the invention

Sodium bicarbonate is NaHCO3 - also called sodium hydrogen carbonate.

The method of the invention comprises the method features cited; it may additionally also include other method features.

Material of value is understood to mean material present in the offgas to be cleaned - for example dusts, or a material comprising such a material - a material comprising such a material may, for example, be material formed from the material present in the offgas to be cleaned via physical reactions - for example adsorption or absorption - or chemical reactions. For example, it may be ore dust discharged in the offgas from a sintering plant. Or it may be a material comprising the ore dust, for example said ore dust adsorbed on a substance added to the offgas for offgas cleaning, for instance activated carbon.

A material of value is a material suitable for feeding into a primary process or for utilization in a primary process for the purpose of increasing the yield or forming the product of the primary process. The aim is to feed materials of value to a utilization for the purpose of a more environmentally benign and less resource-intensive mode of operation, for example in the primary process that produces the offgas subjected to the cleaning operation. The materials of value are, for example, materials added to the primary process for the purpose of product formation therefrom - for example ore dust in the offgas from a sintering process; iron ore dust in the case of iron ore sintering. Materials of value in the offgas may, for example, leave the primary process without conversion to the desired product - for example ore dust from a sintering process - or be discharged with the offgas after conversion to the desired product - for example sintered dust from a sintering process. It is resource-conserving and hence environmentally and economically viable to feed materials of value in offgases from primary processes in a simple manner to utilization in the circuit of economic value, rather than to treat them as waste and hence discharge them from the circuit of economic value. Recirculation of materials of value should be considered to be feeding into a primary process within the scope of this application.

A primary process is understood to mean a process in which an offgas to be cleaned is obtained when the product of the primary process is produced; the product of the primary process is understood to mean the physical product thereof, not including heat or electricity as product. The primary process is one in the metallurgical industry; it may, for example, be the operation of a sintering plant, the operation of a pelletizing plant, the operation of a steelworks converter, for example by the LD/BOF method, or the operation of an EAF (electric arc furnace).

In a sodium bicarbonate-based offgas cleaning operation applied to an offgas stream from a primary process, solid material also called solid deposition product - is separated out of the cleaned offgas. This comprises, for example, dusts from the primary process - for example ash, iron oxides, unconsumed sodium bicarbonate, sodium carbonate, substances formed through chemical reaction with components of the offgas stream - for example sodium sulfate, or other material introduced into the offgas stream for offgas cleaning - or reaction products thereof with components of the offgas stream. The latter material is, for example, adsorption material that contributes to cleaning by adsorption - for example activated carbon.

At least a portion of the solid deposition product is combined with dissolution water; it is also possible to combine the entirety of the solid deposition product with dissolution water. For example, of 100 kg of the solid deposition product, only kg, or only 95 kg, or the entire 100 kg is combined with dissolution water. The portion is either of the same composition as the entire solid deposition product, or it may differ in terms of composition; it may, for example, be enriched or depleted with regard to particular particle sizes or densities by comparison with the average composition of the overall solid deposition product.

The combination with dissolution water can be effected batchwise or continuously.

Combination with dissolution water gives rise to a heterogeneous substance mixture of liquid and solids composed of water insoluble material that are finely distributed therein - a suspension. Combination with dissolution water results in substantial removal of the water-insoluble material, and gives an aqueous starting solution. Substantial removal is understood to mean that at least 70% by mass, preferably at least 90% by mass, of the water-insoluble constituents of the solid deposition product combined with dissolution water is removed; the aqueous starting solution, after the removal, may also contain water-insoluble material to a small degree, for example in the form of suspended matter. It is advantageous to remove as much water-insoluble material as possible since water insoluble material may contain materials of value and may be suitable for recycling into the primary process, or because it can impair the effectiveness and/or efficiency of downstream treatment steps. Examples of methods that can be used for substantial removal include filtration - optionally under pressure, sedimentation, centrifugation; depending on the method, it is possible to remove water-insoluble constituents with different degrees of thoroughness using an economically acceptable level of resources.

The aqueous starting solution obtained in the removal is subjected to multiple successive treatment steps.

It is subjected to at least two treatment steps; these may belong to the same mode of treatment or different modes of treatment.

It is also possible to conduct multiple treatment steps in one mode of treatment or multiple modes of treatment.

In one execution variant, at least one treatment step is conducted batchwise - for example filtration. In this case, buffer capacity should be provided in the upstream and downstream treatment steps - for example by provision of buffer vessels.

In a preferred execution variant, all treatment steps follow one another in a continuous progression. This enables more compact and economic designs since it is possible to dispense with buffer vessels for batchwise operation, and can be controlled more easily. It may be necessary to provide redundant systems in order to be able to conduct process steps continuously in plant components that are not continuously operable - for example filter presses. It is preferable that the starting solution undergoes the treatment steps continuously until the limit is attained.

According to the invention, treatment steps is conducted until the defined limit for the product solution obtained after undergoing the treatment steps is attained.

According to the invention, there is monitoring - by measurement - of one or more limit-relevant parameters, and the treatment steps are controlled on the basis of the monitoring results. Advantageously, in the monitoring by measurement, the scan rate of the measurement is chosen for the one or more limit-relevant parameters such that variances from the limit that are expected or have occurred and an associated requirement for control can be recognized in good time. In one variant, for monitoring, measurements are conducted at least at regular time intervals, i.e. continuously. The time intervals in which measurements are needed to enable adequate control depend on the inertia of the respective treatment steps. The time intervals in which measurement should be effected also depend on the evaluation time. The time intervals in which measurement is effected also depend on the time required for the evaluation. The time intervals in which measurement is effected may also depend on the nature of officially defined limits - for example, averages over time may be required, or spot measurements may be required. Limit-relevant parameters can be obtained by measurement in the product solution and/or by measurement in the starting solution and/or by measurement while undergoing treatment steps, or before and/or after a treatment step. If the limit, for example, defines a concentration of fluoride ions, the measurement of the limit-relevant parameter of fluoride ion concentration can be effected in the starting solution and in the product solution, or in the starting solution and after undergoing a treatment step - followed by other treatment steps - for reduction thereof.

According to the invention, at least a portion - of the water-insoluble material obtained in the removal, and/or - of a solid material obtained in the treatment steps, and/or - of a solid material present from one or more products from one or more of the treatment steps is fed to the first primary process and/or to another primary process.

The water-insoluble material or solid material, with an appropriate moisture content, may also be a sludge.

In the feeding operation, entry into the envisaged primary process may also be preceded by processing steps, for example in order to make the material more easily transportable - for example compacting to give briquets or pellets, or in order to concentrate the materials of value. In the feeding operation, entry into the envisaged primary process may also be preceded by combination with other material, and then the combined volume may be fed in.

The other primary process is a primary process in the metallurgical industry, comprising, for example, ore processing, metal production, iron production, steel production, for example the operation of a sintering plant, the operation of a pelletizing plant, the operation of a steelworks converter, for example by the LD/BOF method, or the operation of an EAF (electric arc furnace).

In this way, it is possible to utilize materials of value present in solid deposition products. This is environmentally friendly and economically advantageous since it can firstly reduce the raw material input in the primary processes and secondly reduce the resources required for disposal.

At least a portion is recycled. For example, all of 100 kg may be recycled, or at least 95% may be recycled, or a portion of % or more may be recycled, or only a portion of 80 kg, or it is possible to recycle merely a portion with a grain size above a particular limit, or it is possible to recycle, for example, only a portion of a particular kind - for example a portion of the "activated carbon-based material" kind.

If the product obtained in one or more treatment steps is not a solid but a liquid product, this may optionally be treated subsequently such that solid material is obtained. This can be accomplished, for example, by chemical treatment - for example precipitation - or physical treatment - for example adsorption onto or absorption into solid particles.

The treatment steps are preferably chosen from at least one member of the group of modes of treatment consisting of - chemical treatment, - mechanical treatment,

- physical treatment.

Chemical treatment is based on chemical reactions with added reagents to form new substances; for example oxidations or formation of salts. Chemical treatment steps are, for example, adjustment of pH, oxidation with, for example, hydrogen peroxide or a hypochlorite, ion exchange.

Physical treatment is based on physical processes, for example adsorption or evaporation. Physical treatment steps are, for example, sedimentation, adsorption by contacting with added activated carbon or other adsorbents, for example zeolites, concentration by evaporation or osmosis.

Mechanical treatment is likewise based on physical processes, but also additionally includes action or application of force. Mechanical treatment steps are, for example, filtration, for instance membrane filtration - for example ultrafiltration, sand filtration, for example under pressure - for example in chamber filter presses, or under the action of gravity - for example filtration without pressure or sedimentation, or centrifugal force - for example centrifugation.

A treatment step may also combine several modes of treatment, for example a heavy metal deposition with sulfides - for example organosulfides - with chemical reaction and with sedimentation, or heavy metal deposition with ion exchange - for example on anionic polymer - with chemical reaction and sedimentation, or other precipitations based on chemical reactions and with addition of flocculant, or precipitation by means of flocculant with adsorption and sedimentation.

In a preferred embodiment, the product solution is released into the environment - for example introduced into water bodies, when its composition has been rendered correspondingly harmless as a result of the treatment steps.

In order to enable unproblematic release into the environment, among other reasons, the starting solution is subjected to multiple successive treatment steps. The aim is that a limit specification be attained for the resultant product solution after it has undergone the treatment steps. The limit specification may relate, for example, to the content of an individual substance present in the starting solution - or multiple substances present in the starting solution, for example concentration of heavy metal ions or heavy metal containing ions, concentration of fluoride or fluoride containing ions, concentration of phosphates or phosphate containing ions, concentration of halides or halide-containing ions, concentration of dioxins, concentration of aromatics, concentration of PCBs; it may also relate to a quality criterion - or multiple quality criteria - such as COD (chemical oxygen demand) or TOC (total organic carbon) or TN (total nitrogen) or pH. The limit specification is set by the operator of the process, for example based on legal requirements.

In a preferred embodiment, the dissolution water, on combination of the solid deposition product with dissolution water, comprises wastewater from a wet offgas cleaning operation. This may be an upstream wet offgas cleaning operation applied to the offgas, or a wet offgas cleaning operation applied to another offgas from the same primary process, or a wet offgas cleaning operation applied to an offgas from another primary process. Such a further utilization of wastewater from a wet offgas cleaning operation makes the method of the invention advantageous in a resource-conserving, environmentally friendly and economic manner.

In a preferred embodiment, at least one treatment step is effected for reduction of dissolved heavy metal ions or dissolved heavy metal-containing ions. Reduction should be understood here to mean reducing the content.

In a preferred embodiment, at least one treatment step is effected for reduction of the COD. Reduction should be understood here to mean reducing the level.

In a preferred embodiment, at least one treatment step is effected for reduction of the TOC. Reduction should be understood here to mean reducing the level.

In a preferred embodiment, at least one treatment step is effected for establishment of a desired pH.

In a preferred embodiment, at least one treatment step is effected for reduction of dissolved fluoride or dissolved fluoride-containing ions. Reduction should be understood here to mean reducing the content. In this treatment step, for example, fluoride is precipitated by addition of, for example, aluminum chloride - this separates out a majority of the fluoride present in the starting solution.

In a preferred embodiment, at least one treatment step is effected by means of ion exchange material. The ion exchange material is preferably regeneratable. By means of ion exchange material, for example, the content of fluoride, nitrate is lowered. Use of selective ion exchange material permits controlled lowering.

In a preferred embodiment, at least one treatment step is effected for reduction of total nitrogen TN. Reduction should be understood here to mean reducing the level.

This can be accomplished, for example, by addition of sodium hypochlorite and subsequent filtration with an activated carbon filter.

In a preferred embodiment, the product solution is used for a different method - i.e. not in the primary process that produces the offgas to be cleaned - as raw material source, especially when its composition is favorable for the respective method. For example, it is possible - for example by means of thermal treatment by evaporation - to concentrate the product solution and hence to fractionally crystallize different substances and hence to make them utilizable.

For example, it is thus possible to obtain soda or sodium bicarbonate from the product solution, which can be utilized, for example, for sodium bicarbonate-based offgas cleaning.

The present application further provides a signal processing device with a machine-readable program code, characterized in that it includes control commands for performance of a method of the invention.

The present application further provides a machine-readable program code for a signal processing device, characterized in that the program code includes control commands that cause the signal processing device to perform a method of the invention.

The present application further provides a storage medium having a machine-readable program code of the invention stored thereon.

The present application further provides an apparatus for performing a method of the invention. It is an apparatus for recirculating materials of value in solid deposition product from an adsorptive and sodium bicarbonate-based offgas cleaning operation applied to offgas from a first primary process including deposition of a solid deposition product, comprising - at least one dissolution vessel for combination of solid deposition product with dissolution water, into which at least one deposition product addition conduit and at least one dissolution water feed open, - at least one outlet proceeding from the dissolution vessel for discharge of suspension from the dissolution vessel, - at least one deposition apparatus for removal of water insoluble material from the suspension to produce a starting solution, wherein the outlet opens into the deposition apparatus, - at least one treatment apparatus for performance of multiple successive treatment steps for production of a product solution, - at least one starting solution conduit proceeding from the deposition apparatus for introduction of starting solution into the treatment apparatus, - at least one product solution outlet proceeding from the treatment apparatus, - at least one monitoring device for detection of at least one parameter at least in the product solution, connected to at least one closed-loop control device suitable for closed-loop control of the treatment apparatus on the basis of results from the monitoring device, - at least one feed apparatus for feeding solid material to the first primary process and/or to another primary process.

Optionally present upstream of the dissolution vessel in each case are one or more buffer vessels for dissolution water or for solid deposition product - i.e. virtually in the dissolution water feed or in the deposition product addition conduit.

Optionally present downstream of the dissolution vessel in each case are one or more buffer vessels for suspension - i.e.

virtually in the outlet. Optionally present downstream of the deposition apparatus in each case are one or more buffer vessels - i.e. virtually in the starting solution conduit. Optionally present downstream of the treatment apparatus in each case are one or more buffer vessels - i.e. virtually in the product solution outlet. It is also possible for buffer vessels to be provided in the treatment apparatus.

By means of the buffer vessels, it is possible to mutually connect parts of the method procedure that run at different speeds, enabling a continuous method.

The treatment apparatus comprises multiple treatment units for performance of multiple successive treatment steps for performance of a product solution.

It is preferably suitable for performance of multiple successive treatment steps from at least one member of the group of modes of treatment consisting of - chemical treatment, - mechanical treatment, - physical treatment.

For each treatment step, one or more treatment units may be provided, which may be arranged in sequence or in parallel.

For example, it may be envisaged for a treatment step for reduction of the COD to use two treatment units in which different steps for reduction of the COD are undertaken successively. For example, for a treatment step in order to reduce the content of dissolved heavy metal ions or dissolved heavy metal-containing ions, the use of three treatment units may be envisaged - for example one treatment unit to establish a desired pH, one treatment unit for precipitation, and one treatment unit to draw off precipitated material. Precipitated material may, for example - optionally after subsequent dewatering, or in the dried state - be recycled into a primary process or sent to landfill. It may thus be the case that a treatment unit for drawing off precipitated material is part of a feed apparatus.

It would also be possible, for example for the adjustment of pH, to provide two or more treatment units in a parallel arrangement that are fed by a common conduit for liquid to be treated, and to release the products thereof into a common conduit for the purpose of feeding to downstream treatment steps or treatment units. Corresponding parallel or sequential arrangement is also possible for other treatment units or treatment steps. Starting solution enters the first treatment unit viewed in flow direction from the dissolution vessel to the product solution outlet; the liquid product from the preceding treatment unit enters the downstream treatment units in each case. Product solution emerges from the last treatment unit viewed in flow direction from the dissolution vessel to the product solution outlet.

Reagent feeds optionally open into the respective treatment units, which serve for controllable feeding of the reagents required for the respective treatment from corresponding reagent storage vessels.

The treatment apparatus preferably comprises at least one treatment unit for reduction of dissolved heavy metal ions or dissolved heavy metal-containing ions.

The treatment apparatus preferably comprises at least one treatment unit for reduction of the COD.

The treatment apparatus preferably comprises at least one treatment unit for reduction of the TOC.

The treatment apparatus preferably comprises at least one treatment unit for establishment of a desired pH.

The treatment apparatus preferably comprises at least one treatment unit for reduction of dissolved fluoride or dissolved fluoride-containing ions.

The treatment apparatus preferably comprises at least one treatment unit comprising ion exchange material. The apparatus of the invention preferably also comprises apparatuses for regeneration of the ion exchange material.

The treatment apparatus preferably comprises at least one treatment unit for reduction of total nitrogen - TN.

The treatment apparatus preferably comprises at least one apparatus for removal of solids, for example filter.

The monitoring device is suitable for detecting at least one parameter, at least in the product solution. It is also possible to detect multiple parameters in the product solution and/or one or more parameters in one or more of the treatment steps. The control device is suitable for controlling the treatment apparatus on the basis of results from the monitoring device; the method of control here may, for example, be control of individual treatment units. The control device is correspondingly connected to the monitoring device for transmission of results.

It is also possible for there to be multiple monitoring devices, each of which may monitor a single parameter or multiple parameters. It is also possible for there to be multiple control devices, each of which may control a single parameter or multiple parameters.

The monitoring devices and control devices may also be integrated collectively into one apparatus.

The feed apparatus is suitable for supply of solid material to the first primary process and/or to another primary process. It is suitable for feeding at least a portion - of the water-insoluble material obtained in the removal, and/or - of a solid material obtained in the treatment steps, and/or - of a solid material present from one or more products from one or more of the treatment steps, to the first primary process and/or to another primary process.

For this purpose, it may comprise, for example, conveying devices and/or conduits. Conduits may proceed, for example, from the relevant sites of formation of the solid materials or of the water-insoluble material - in the case of water-insoluble material obtained in the course of removal, the site of formation is understood to mean the site of removal - and lead to apparatuses for performance of the (first) primary process and/or another primary process. Conveying devices may be provided, for example, in order to move solid material within the conduits. Conveying devices may also comprise conveyor belts, or comprise movable vessels that receive solid material at the sites of formation in question for the solid materials and - optionally after intermediate storage, for example at a storage site or in vessels, containers or in silos - lead to devices for performance of the first primary process and/or another primary process.

The feed apparatus may comprise, for example, apparatuses for storage of solid material.

The feed apparatus may comprise, for example, apparatuses for storage of products from treatment steps.

The feed apparatus may comprise, for example, apparatuses for obtaining solid material from products from treatment steps.

Storage may be provided, for example, when the feeding of solid material to the first primary process and/or to another primary process is not to be continuous but batchwise, and, therefore, buffering of the amounts obtained is necessary. The feed apparatus may comprise, for example, apparatuses for processing, for example for concentration of materials of value.

The feeding can be effected via direct connections of the treatment apparatus and/or the deposition apparatus to the primary process or - for example in the presence of storage apparatuses for buffering of the amounts obtained, or in the presence of processing apparatuses that serve for further processing, for example concentration, of material to be recycled - via indirect connections of the treatment apparatus and/or the deposition apparatus to the primary process.

Such an apparatus can be used to perform a method of the invention.

Brief description of the drawings

The invention is elucidated by schematic illustrative diagrams of embodiments.

Figure 1 shows, using a schematic of one embodiment, the general scheme for the sequence of a method of the invention in an apparatus of the invention.

Figure 2 shows a treatment apparatus as may be executed in figure 1 in more detail.

Figure 3 shows a schematic of an apparatus for performance of a method of the invention in connection with a first primary process.

Description of embodiments

Examples

Figure 1 shows, with reference to one embodiment, in schematic form, the sequence of a method of the invention in an apparatus of the invention.

Solid deposition product 1 from an adsorptive and sodium bicarbonate-based offgas cleaning operation in a primary process is directed via a deposition product addition conduit 2 into a dissolution vessel 3, where it is combined with dissolution water from a dissolution water feed 4. The suspension formed in the dissolution vessel 3 is fed via the outlet 5 from a deposition apparatus 6, shown here schematically as a filter. A buffer vessel 20 for suspension which is optionally present in the outlet 5 is shown outlined with dotted lines. By means of deposition apparatus 6, water-insoluble material is largely removed; in the case shown with a filter, at least 90% by mass of the water-insoluble material is removed. The aqueous starting solution obtained in the removal is introduced into a treatment apparatus 8 via the starting solution conduit 7a. It would be possible for buffer vessels to be disposed in the starting solution conduit 7a between the filter and treatment apparatus, which is not shown specially for better clarity.

What is shown is a material outlet 7b proceeding from the deposition apparatus 6 - i.e. the site of formation of the water insoluble material for the purposes of the present application. It is part of a feed apparatus. For better clarity, it is not shown specially where the feed leads. The feed apparatus may recirculate the water-insoluble material, for example into the primary process from which the offgas to be cleaned originates; this is shown schematically in figure 3.

The treatment apparatus 8 serves to perform multiple successive treatment steps from at least one member of the group of modes of treatment consisting of - chemical treatment, - mechanical treatment, - physical treatment. The treatment steps produce a product solution 9 which is discharged from the treatment apparatus 8 via the product solution outlet 10a.

The material outlet 10b symbolizes one or more conduits that proceed from the sites of formation of solid materials in the course of the treatment steps. It is/they are parts of a feed apparatus. For better clarity, it is not shown specially where the feeds lead; the feed apparatus may recirculate the solid material, for example into the primary process from which the offgas to be cleaned originates; this is shown schematically in figure 3. The properties of the product solution 9 are to attain a defined limit - for example with multiple parameters to be achieved. A monitoring device 11 monitors the parameters in the product solution 9 that are of relevance for the defined limit, shown schematically by a straight monitoring conduit. The treatment steps conducted in the treatment apparatus 8 are controlled on the basis of the results of the monitoring by a control device 12, shown schematically by a wavy connection to the treatment apparatus that proceeds from the control device 12. Transmission of monitoring results to the control device 12 is illustrated schematically by a connection between control device 12 and monitoring device 11. The product solution may be released into the environment, for example, shown schematically by arrow A, and/or used as raw material source, shown schematically by arrow B.

Figure 2 shows a schematic of a variant of the sequence in a treatment apparatus 8.

The treatment apparatus 8 comprises multiple treatment units for performance of multiple successive treatment steps for production of the product solution 9. For the treatment step U, reduction of the COD, two treatment units 13 and 14 in sequential arrangement are present. For better clarity, the diagram does not show the feeding of the iron(II) sulfate FeSO 4 , sulfuric acid H 2 SO4 and hydrogen peroxide H 2 0 2 reagents from corresponding reagent storage vessels via reagent feeds. Starting solution enters the first treatment unit 13 viewed in flow direction from the dissolution vessel 3 toward the product solution outlet 10. The liquid product from the upstream treatment unit 13 enters the downstream treatment unit 14.

The treatment step U is followed by the treatment step V in the treatment unit 15, shown here as optional fluoride precipitation with a dotted outline. For better clarity, the diagram does not show the feeding of the aluminum chloride AlCl 3 reagent from corresponding reagent storage vessels via reagent feeds.

The treatment step V is followed by the treatment step W for reduction in the content of dissolved heavy metal ions or dissolved heavy metal-containing ions. For this purpose, as a minor treatment step in treatment unit 16, the pH is adjusted by adding sodium hydroxide solution NaOH, and precipitation is induced by addition of organic sulfides, which is continued in treatment unit 17 by addition of anionic polymer. In treatment unit 18a, for example in treatment unit 16 and/or 17, suspended solid material formed by precipitation and precipitated material are very substantially removed. For better clarity, the diagram does not show the feeding of the reagents from corresponding reagent storage vessels via reagent feeds.

Solid material is sent to a destination via the material outlet 18b which proceeds from the treatment unit 18a and is part of a feed apparatus. For better clarity, it is not shown specially where the feed leads. The feed apparatus may recirculate the water-insoluble material, for example into the primary process from which the offgas to be cleaned originates; this is shown schematically in figure 3, since the material outlet 18b may correspond to the material outlet 10b.

The liquid product from the treatment unit 18a enters treatment unit 19 in which treatment step X, reduction of total nitrogen - TN, is conducted. For better clarity, the diagram does not show the feeding of the sodium hypochlorite reagent, NaOCl, from corresponding reagent storage vessels via reagent feeds.

Filtration is effected in the subsequent treatment step Y, wherein an activated carbon filter is also used. In the subsequent treatment step Z, by means of ion exchange, the fluoride content in the filtrate from the treatment step Y is reduced.

This affords the product solution 9.

Treatment steps X and Z are optional and therefore have a dotted outline.

Figure 3 shows a schematic of a first primary process 21, for example a sintering process, the offgas from which is subjected to an adsorptive and sodium bicarbonate-based offgas cleaning operation in offgas conduit 22. Discharge of cleaned offgas is symbolized by a wavy arrow that branches off from conduit 22. Solid deposition product from this offgas cleaning operation is treated as shown in figure 1; this is symbolized in figure 3 in that the offgas conduit 22 opens into rectangle 23; rectangle 23 symbolizes the content of figure 1. A feed apparatus 24 is symbolized by the material outlets 7b and 10b; these correspond to the conduits addressed in figure 1. The storage apparatus 25 and processing apparatus 26 that are optionally present in these conduits of the feed apparatus are shown by dotted lines.

The description of advantageous configurations of the invention that has been given so far contains numerous features that are reproduced in the individual subsidiary claims, in some cases with several combined. However, these features may appropriately also be considered individually and be combined to give viable further combinations. In particular, these features are each combinable individually and in any suitable combination in a method of the invention.

Even though the description and the claims use some terms respectively in the singular or in connection with a number, the scope of the invention for these terms shall not be limited to the singular or the respective number. Moreover, the word "a" shall be considered not to mean the number one but to mean the indefinite article.

The properties, features and advantages of the invention as described, and the manner in which they are achieved, become more clearly and distinctly comprehensible in connection with the description of the working example(s) of the invention, which are elucidated in detail in connection with the drawings. The working example(s) serve(s) to elucidate the invention and do not limit the invention to combinations of features specified therein, not even in relation to functional features. Moreover, suitable features of each working example may also explicitly be considered in isolation, removed from a working example, introduced into another working example for supplementation thereof, and combined with any of the claims.

Even though the invention has been illustrated and described in detail by virtue of the preferred working example(s), the invention is not limited by the example(s) disclosed, and other variations may be inferred therefrom without leaving the scope of protection of the invention according to the claims.

List of reference numerals

1 Solid deposition product 2 Deposition product addition conduit 3 Dissolution vessel 4 Dissolution water feed Outlet 6 Deposition apparatus 7a Starting solution conduit 7b Material outlet 8 Treatment apparatus 9 Product solution a Product solution outlet b Material outlet 11 Monitoring device 12 Control device 13 Treatment unit 14 Treatment unit Treatment unit 16 Treatment unit 17 Treatment unit 18a Treatment unit 18b Material outlet 19 Treatment unit Buffer vessel 21 Primary process 22 Offgas conduit 23 Rectangle 24 Feed apparatus

U Treatment step V Treatment step W Treatment step X Treatment step Y Treatment step

Z Treatment step

Claims

1) A method of recirculating materials of value in solid deposition product of an adsorptive and sodium bicarbonate-based offgas cleaning operation applied to offgas from a first primary process in the metallurgical industry including deposition of a solid deposition product, wherein combination of at least a portion of the solid deposition product with dissolution water results in substantial removal of water-insoluble material, which is characterized in that it comprises subjecting the aqueous starting solution obtained in the removal to multiple successive treatment steps until a limit specification is attained for a product solution obtained after implementation of the treatment steps, wherein one or more limit-relevant parameters are monitored and the treatment steps are controlled on the basis of the monitoring results, and wherein at least a portion - of the water-insoluble material obtained in the removal, and/or - of a solid material obtained in the treatment steps, and/or - of a solid material present from one or more products from one or more of the treatment steps is fed to the first primary process and/or to another primary process in the metallurgical industry.

2) The method as claimed in claim 1, characterized in that the first primary process and/or the other primary process is the operation of a member of the group consisting of

- sintering plant, - pelletizing plant, - steelworks converter, - EAF.

3) The method as claimed in claim 1 or claim 2, characterized in that the feeding includes processing steps.

4) The method as claimed in any of claims 1 to 3, characterized in that the treatment steps are chosen from at least one member of the group of modes of treatment consisting of - chemical treatment, - mechanical treatment, - physical treatment.

) The method as claimed in any of claims 1 to 4, characterized in that the product solution is released into the environment.

6) The method as claimed in any of claims 1 to 5, characterized in that the dissolution water comprises wastewater from a wet offgas cleaning operation.

7) The method as claimed in any of claims 1 to 6, characterized in that at least one treatment step is effected for reduction of dissolved heavy metal ions or dissolved heavy metal containing ions.

8) The method as claimed in any of claims 1 to 7, characterized in that the product solution is used as raw material source for a different process.

9) An apparatus for recirculating materials of value in solid deposition product from an adsorptive and sodium bicarbonate based offgas cleaning operation applied to offgas from a first primary process including deposition of a solid deposition product, comprising - at least one dissolution vessel for combination of solid deposition product with dissolution water, into which at least one deposition product addition conduit and at least one dissolution water feed open, - at least one outlet proceeding from the dissolution vessel for discharge of suspension from the dissolution vessel, - at least one deposition apparatus for removal of water insoluble material from the suspension to produce a starting solution, wherein the outlet opens into the deposition apparatus, - at least one treatment apparatus for performance of multiple successive treatment steps for production of a product solution, - at least one starting solution conduit proceeding from the deposition apparatus for introduction of starting solution into the treatment apparatus, - at least one product solution outlet proceeding from the treatment apparatus, - at least one monitoring device for detection of at least one parameter at least in the product solution, connected to at least one closed-loop control device suitable for closed-loop control of the treatment apparatus on the basis of results from the monitoring device, - at least one feed apparatus for feeding solid material to the first primary process and/or to another primary process.

) The apparatus as claimed in claim 9, characterized in that the treatment apparatus comprises at least one treatment unit for reduction of dissolved heavy metal ions or dissolved heavy metal-containing ions.

11) The apparatus as claimed in claim 9 or claim 10, characterized in that the treatment apparatus comprises at least one apparatus for removal of solids.

12) The apparatus as claimed in any of claims 9 to 11, characterized in that the feed apparatus comprises apparatuses for storage of solid material.

13) The apparatus as claimed in any of claims 9 to 12, characterized in that the feed apparatus comprises apparatuses for obtaining solid material from products from treatment steps.

14) The apparatus as claimed in any of claims 9 to 13, characterized in that the feed apparatus comprises apparatuses for processing.