Method for reducing iron containing particles, apparatus for cleaning an introduction gas stream, system comprising such an apparatus and use of such an apparatus or a system

Abstract

The invention relates to a method for reducing iron containing particles (105) comprised in an introduction gas stream (101), wherein the method comprises the following steps: - introducing the introduction gas stream (101) to a reducing volume (20); - at least temporarily retaining at least a part of the iron containing particles (105) in the reducing volume (20); and - reducing at least part of the retained iron containing particles (105) increasing their degree of reduction. The invention further relates to an apparatus (10) for cleaning an introduction gas stream (101) containing iron containing particles (105) and a system (100) comprising such an apparatus (10) and a direct reduction reactor (30).

Description

[0001] Seite 1 / 40

[0002] Anmelder : Paul Wurth S .A.

[0003] Unser Zeichen: P81090WO

[0004] Method for reducing iron containing particles , apparatus for cleaning an introduction gas stream, system comprising such an apparatus and use of such an apparatus or a system

[0005] The present invention relates to a method for reducing iron containing particles, an apparatus for cleaning an introduction gas stream, a system for comprising such an apparatus and a use of such an apparatus or a system.

[0006] In a direct reduction reactor, an off-gas stream at the outlet of the reactor typically contains entrained fine particles, particularly iron containing particles, which need to be separated from the off-gas stream in order to further use the off-gas in other process steps or to refeed the off-gas to the direct reduction process . Such iron containing particles are typically characterized by being on average finer than particles initially introduced to the direct reduction reactor as feed material and being of a lower degree of reduction than the product stream leaving the direct reduction reactor .

[0007] It is common practice to install gas cleaning devices in the off-gas stream such as cyclones or washers or combinations thereof to remove iron containing particles from the off-gas stream. However, with these gas cleaning devices, limitations in gas cleaning efficiency remain. Cyclones have a certain collecting limit in terms of a minimal particle size as well as a particle size distribution due to the collecting mechanism of a cyclone itself . Washers, which are typically used to cool the off-gas stream of a direct reduction reactor, can be used to further remove fine particles from the off-gas stream, whichSeite 2 / 40

[0008] P81090WO cannot be removed from the off-gas stream using cyclones . However, these particles are taken out of the process as sludge and are either dumped or must be de-watered before further usage such as refeeding them to the direct reduction process can be possible . The resulting sludge after a washer thus incur additional costs for de-watering, drying, re-heating, and complex material handling when the sludge is to be used internally. Thus, the efficiency of the cleaning steps is limited in particular when there is a high amount of fines and / or wide particle size distribution of the feed material initially fed to the direct reduction reactor . Further, even if the fine particles are to be used internally within the process itself either directly after a cyclone or after a washer, the particles cannot be directly fed to the product stream due to their lower degree of reduction. This generally requires an additional reduction step for these fine particles . Alternatively, the fine particles can be refed to the direct reduction reactor, potentially increasing their degree of reduction to a point, where the fine particles can be fed to the product stream. This circulation of fine particles in the direct reduction process however occupies reduction volume of the direct reduction reactor thus decreasing overall yield and efficiency of the reduction process .

[0009] An underlying task of the present invention is to provide a method that is capable of increasing an overall yield and efficiency of a direct reduction process .

[0010] This problem underlying the present invention is solved by a method according to claim 1 . Advantageous embodiments are described in the dependent claims .

[0011] According to a first aspect of the present invention, the problem underlying the present invention is solved by a method for reducing iron containing particles comprised in an introduction gas stream, wherein the method comprises the following steps :Seite 3 / 40

[0012] P81090WO introducing the introduction gas stream to a reducing volume ;

[0013] at least temporarily retaining at least a part of the iron containing particles in the reducing volume; and reducing at least part of the retained iron containing particles increasing their degree of reduction.

[0014] A method designed in such a way has the advantage of, removing iron containing particles from a gas stream and at the same time increasing a reduction degree of the iron containing particles removed from the gas stream and retained in the reducing volume .

[0015] A reducing volume preferably is any volume, particularly an at least partially limited volume, a gas stream, particularly the introduction gas stream, can enter and the same or another gas stream can exit . The reducing volume may also be referred to as reducing and cleaning volume .

[0016] The method may comprise a step of maintaining a reducing volume temperature of greater than or equal to 300 °C, particularly of greater than or equal to 450 °C, preferably of greater than or equal to 500 °C, preferred of greater than or equal to 600 °C, and particularly preferred of greater than or equal to 650 °C . The method may comprise a step of maintaining a reducing volume temperature of lower than or equal to 1100 °C, particularly of lower than or equal to 950 °C, preferably of lower than or equal to 850 °C, and preferred of lower than or equal to 800 °C .

[0017] According to a preferred embodiment, the method may comprise a step of maintaining a reducing volume temperature of greater than or equal to 350 °C and lower than or equal to 1050 °C, particularly of greater than or equal to 500 °C and lower than or equal to 900 °C .Seite 4 / 40

[0018] P81090WO The reducing volume temperature is preferably the temperature of the reducing volume, particularly the temperature of the gas and / or gas composition of the reducing volume . Particularly, iron containing particles retained in the reducing volume may comprise a temperature different from the reducing volume temperature . Alternatively, iron containing particles retained in the reducing volume may comprise the reducing volume temperature .

[0019] The method may comprise a step of maintaining a reducing volume composition with a hydrogen content of greater than or equal to 50 vol . -%, particularly greater than or equal to 60 vol . -%, preferably greater than or equal to 70 vol . -%, and particularly preferred greater than or equal to 75 vol . -% . The method may comprise a step of maintaining a reducing volume composition with a hydrogen content of lower than or equal to 100 vol . -%, particularly lower than or equal to 90 vol . -%, preferably lower than or equal to 85 vol . -%, and particularly preferred lower than or equal to 80 vol . -% .

[0020] The reducing volume composition is preferably the gas composition in the reducing volume . In other words, gas composition specifications in vol . -% typically do not include iron containing particles retained in the reducing volume . For example, a reducing volume composition with a hydrogen content of greater than or equal to 50 vol . -% means, that the gas composition in the reducing volume has a hydrogen content of greater than or equal to 50 vol . -%, regardless of the amount of iron containing particles retained in the reducing volume .

[0021] By reducing at least part of the iron containing particles, an iron content of the iron containing particles is increased. In other words, reducing in the context of the invention is to be understood as the chemical process of reducing, lowering an oxidization state of a particle .Seite 5 / 40

[0022] P81090WO

[0023] An iron content may be the amount of iron in wt . -% and / or in vol . -% and / or in mol . -% of a particle and / or a plurality of particles . Accordingly, the degree of reduction may refer to an amount of iron in wt . -% and / or in vol . -% of a particle and / or a plurality of particles .

[0024] According to a preferred embodiment, the degree of reduction refers to the ratio of oxygen to iron content in mol . -% of a particle and / or a plurality of particles . Particularly, the degree of reduction may be calculated according to DIN ISO 11258 : 2015.

[0025] According to a preferred embodiment, the following formula ( 1 ) may be used:

[0026]

[0027] wherein

[0028] RD = degree of reduction,

[0029] 0 = total amount of oxygen bonded on iron in mol, and Fetot = total amount of iron in the sample in mol .

[0030] The degree of reduction in the context of this invention is to be understood as an average degree of reduction of a given sample . For example a sample of 1 kg, 1 cm3or 1 mol of particles .

[0031] The iron containing particles may comprise oxygen. Particularly, the iron containing particles may comprise iron oxide containing particles .

[0032] The introduction gas stream may be a reactor outlet gas stream of a direct reduction reactor, particularly of a fluidized bedSeite 6 / 40

[0033] P81090WO direct reduction reactor . A method designed in such a way has the advantage of increasing an overall yield and efficiency of a direct reduction process by increasing the degree of reduction of the iron containing particles comprised in the introduction gas stream and at the same time cleaning the introduction gas stream from the iron containing particles, enabling a potential refeeding of the introduction gas stream to the direct reduction process .

[0034] The introduction gas stream may be a de-dusting device outlet gas stream, particularly an outlet gas stream exiting a cyclone . A method designed in such a way has the advantage of increasing a degree of reduction of the iron containing particles comprised in the introduction gas stream, particularly a small particles and remaining dust, not removed within the de-dusting device . According to a particular preferred embodiment the introduction gas stream may be a reactor outlet gas stream, wherein the reactor outlet gas stream is introduced into a de-dusting volume before it is introduced into the reducing volume .

[0035] The introduction gas stream may comprise hydrogen and / or water vapor and / or Nitrogen and / or further gases released by the iron containing particles .

[0036] The method may be designed in such a way, that the step of reducing at least part of the retained iron containing particles increases their degree of reduction by at least 1 % compared to their degree of reduction when being introduced to the reducing volume, particularly by at least 5 %, preferably by at least 10 % and particularly preferred by at least 15 % . The method may be designed in such a way, that the step of reducing at least part of the retained iron containing particles increases their degree of reduction by at least 20 % compared to their degree of re-Seite 7 / 40

[0037] P81090WO duction when being introduced to the reducing volume, particularly by at least 25 %, preferably by at least 30 % and particularly preferred by at least 35 % .

[0038] The method may comprise a step of retaining at least part of the iron containing particles in the reducing volume for a time period of greater than or equal to 2 minutes, particularly of greater than or equal to 5 minutes, preferably of greater than or equal to 10 minutes and particularly preferred of greater than or equal to 15 minutes .

[0039] In this way, the increase in degree of reduction of the iron containing particles can be increased and controlled in a better way. The longer the particles are retained in the reducing volume, the more the degree of reduction can be increased. Particularly, a specific degree of reduction of the iron containing particles can be set to a desired target value with an increased accuracy .

[0040] The method may comprise the following step :

[0041] reducing at least part of the retained iron containing particles to a degree of reduction of greater than or equal to 12 %, particularly of greater than or equal to 30 % and preferably of greater than or equal to 50 % .

[0042] A method designed in such a way has the advantage that, particularly when being used for treating a reactor outlet gas stream of a direct reduction reactor, the iron containing particles retained in the reducing volume may be directly fed to a product stream of the direct reduction reactor increasing the yield of the direct reduction process and thus increasing overall efficiency of the direct reduction process .

[0043] The method may comprise the following steps :Seite 8 / 40

[0044] P81090WO discharging a discharging gas stream from the reducing volume, wherein the discharging gas stream contains less iron containing particles than the introduction gas stream introduced to the reducing volume; and / or

[0045] introducing a backflushing gas to the reducing volume; and / or

[0046] pulsatingly or continuously introducing a fluidizing gas to the reducing volume; and / or

[0047] discharging the retained iron containing particles from the reducing volume .

[0048] A method designed in such a way has the advantage that the discharging gas stream may be refed to a direct reduction process, particularly to a fluidized bed direct reduction process, with a reduced amount of additional post gas treatment steps .

[0049] The method may be designed in such a way, that a temperature of the discharging gas stream discharged from the reducing volume is greater than or equal to 250 °C, particularly greater than or equal to 350 °C, preferably greater than or equal to 450 °C, preferred greater than or equal to 550 °C, and particularly preferred greater than or equal to 650 °C . The method may be designed in such a way, that a temperature of the discharging gas stream discharged from the reducing volume is lower than or equal to 1050 °C, particularly lower than or equal to 950 °C, preferably lower than or equal to 850 °C, preferred lower than or equal to 750 °C, and particularly preferred lower than or equal to 700 °C .

[0050] The method may be designed in such a way, that a hydrogen content of the discharging gas stream discharged from the reducing volume is greater than or equal to 40 vol . -%, particularly greater than or equal to 50 vol . -%, preferably greater than or equal to 60 vol . -%, and particularly preferred greater than or equal to 65 vol . -% . The method may be designed in such a way, that aSeite 9 / 40

[0051] P81090WO hydrogen content of the discharging gas stream discharged from the reducing volume is lower than or equal to 95 vol . -%, particularly lower than or equal to 90 vol . -%, preferably lower than or equal to 85 vol . -%, and particularly preferred lower than or equal to 80 vol . -% .

[0052] The method may comprise a step of mixing the discharging gas stream with hydrogen after the discharging gas stream is discharged from the reducing volume .

[0053] The backflushing gas is preferably used to clean one or more than one filtering device arranged in the reducing volume . In this way, a stable amount of iron containing particles can be retained in the reducing volume throughout a continuous process . The backflushing gas may be pulsatingly and / or continuously introduced to the reducing volume . A pulsating flow may comprise one or more than one oscillating velocity component . A pulsating flow may further be achieved by superimposing a stationary basic flow, particularly a continuous flow, with an oscillating velocity component .

[0054] The fluidizing gas is preferably used to improve material handling of the retained iron containing particles discharged from the reducing volume . By introducing a fluidizing gas to the reducing volume clogging of a particle outlet opening for discharging the retained iron containing particles from the reducing volume can be mitigated. The fluidizing gas may be pulsatingly and continuously introduced to the reducing volume .

[0055] The method may comprise a step of increasing an average particle size of at least a part of the retained iron containing particles .

[0056] In this way, the retained iron containing particles can easier be handled upon discharging from the reducing volume . Further,Seite 10 / 40

[0057] P81090WO the average particle size of the retained iron containing particles is closer to a particles size of particles of a product stream, making feeding the retained iron containing particles to the product stream easier .

[0058] Iron containing particles retained in a reducing volume, particularly on a filtering surface of a filtering device, may agglomerate due to increased contact time and reduction work to . In this way, multiple particles may be agglomerated on the filtering surface of the filtering device increasing an average particle size of the iron containing particles .

[0059] The average particle size of the at least part of the retained iron containing particles may be increased to an average particle size of greater than or equal to the average particle size of the iron containing particles comprised in the introduction gas stream introduced to the reducing volume, particularly by an amount of at least 1 % , preferably by an amount of at least 3 %, particularly by an amount of at least 7 % .

[0060] The average particle size mentioned herein is to be understood as the Sauter-Diameter (SMD) . The Sauter-Diameter indicates the ratio of volume to surface area of spheres that would be produced if the entire particle volume of a bulk material were to be molded into spheres of the same size . The Sauter-Diameter may be calculated according to the formula in DIN ISO 9276-2.

[0061] The method may be designed in such a way, that a temperature of the introduction gas stream introduced in the reducing volume is greater than or equal to 300 °C, preferably greater than or equal to 450 °C, preferred greater than or equal to 600 °C .Seite 11 / 40

[0062] P81090WO In this way, a reduction potential of the introduction gas stream can be increased, such that the iron containing particles retained in the reducing volume can be reduced to a higher degree of reduction.

[0063] The method may be designed in such a way, that a temperature of the introduction gas stream introduced in the reducing volume is greater than or equal to 650 °C, preferably greater than or equal to 750 °C, preferred greater than or equal to 850 °C .

[0064] The method may be designed in such a way, that a temperature of the introduction gas stream introduced in the reducing volume is lower than or equal to 1050 °C, particularly lower than or equal to 950 °C, preferably lower than or equal to 850 °C, and preferred lower than or equal to 800 °C .

[0065] The iron containing particles comprised in the introduction gas stream may comprise an average particle size of lower than or equal to 200 pm, particularly of lower than or equal to 150 pm, preferably of lower than or equal to 100 pm, preferred of lower than or equal to 50 pm and particularly preferred of lower than or equal to 25 pm.

[0066] The average particle size mentioned herein is to be understood as the Sauter-Diameter (SMD) .

[0067] The method may be designed in such a way that the introduction gas stream comprises a particle load of greater than or equal to 1 g / m3, particularly of greater than or equal to 10 g / m3, preferably of greater than or equal to 20 g / m3, preferred of greater than or equal to 30 g / m3and particularly preferred of greater than or equal to 40 g / m3. The method may be designed in such a way that the introduction gas stream comprises a particle load of lower than or equal to 50 g / m3, particularly of lower than or equal to 45 g / m3, particularly of lower than or equal to 35 g / m3,Seite 12 / 40

[0068] P81090WO preferably of lower than or equal to 25 g / m3, preferred of lower than or equal to 15 g / m3and particularly preferred of lower than or equal to 5 g / m3.

[0069] The method may be designed in such a way that the introduction gas stream comprises a particle load of greater than or equal to 5 mg / m3, particularly of greater than or equal to 10 mg / m3, preferably of greater than or equal to 20 mg / m3, preferred of greater than or equal to 30 mg / m3and particularly preferred of greater than or equal to 40 mg / m3. The method may be designed in such a way that the introduction gas stream comprises a particle load of lower than or equal to 500 mg / m3, particularly of lower than or equal to 55 mg / m3, particularly of lower than or equal to 45 mg / m3, preferably of lower than or equal to 35 mg / m3, preferred of lower than or equal to 25 mg / m3and particularly preferred of lower than or equal to 15 mg / m3.

[0070] The method may be designed in such a way that the discharging gas stream comprises a particle load of lower than or equal to 12 mg / m3, particularly of lower than or equal to 10 mg / m3, particularly of lower than or equal to 8 mg / m3, preferably of lower than or equal to 5 mg / m3and preferred of lower than or equal to 3 mg / m3.

[0071] A gas having a particle load of greater than, lower than or equal to a specified value in mg / m3means, that one m3of a gas stream under standard temperature and pressure conditions (STP) comprises the specified amount of particles . For example, an introduction gas stream comprising a particle load of lower than or equal to 50 mg / m3means, that one m3of introduction gas stream under standard temperature and pressure conditions (STP) comprises less than or equal to 50 mg of particles .

[0072] The method may be designed in such a way, that a hydrogen content of the introduction gas stream introduced in the reducing volumeSeite 13 / 40

[0073] P81090WO is greater than or equal to 50 vol . -% , particularly greater than or equal to 60 vol . -% , preferably greater than or equal to 70 vol . -% , and particularly preferred greater than or equal to 75 vol . -% . The method may be designed in such a way, that a hydrogen content of the introduction gas stream introduced in the reducing volume is lower than or equal to 100 vol . -% , particularly lower than or equal to 90 vol . -% , preferably lower than or equal to 85 vol . -% , and particularly preferred lower than or equal to 80 vol . -% .

[0074] A hydrogen content of a gas and / or a gas stream is the amount of hydrogen contained in that gas and / or gas stream in vol . -% . Accordingly, a hydrogen content of the introduction gas stream is the amount of hydrogen contained in the introduction gas stream in vol . -% .

[0075] The method may be designed in such a way, that a hydrogen content of the backflushing gas and / or a hydrogen content of the fluidi zing gas introduced in the reducing volume is / are greater than or equal to 50 vol . -% , particularly greater than or equal to 60 vol . -% , preferably greater than or equal to 70 vol . -% , and particularly preferred greater than or equal to 75 vol . -% . The method may be designed in such a way, that a hydrogen content o f the backflushing gas and / or the fluidi zing gas introduced in the reducing volume is / are lower than or equal to 100 vol . -% , particularly lower than or equal to 90 vol . -% , preferably lower than or equal to 85 vol . -% , and particularly preferred lower than or equal to 80 vol . -% .

[0076] A hydrogen content of the backflushing gas is the amount of hydrogen contained in the backflushing gas in vol . -% . A hydrogen content of the fluidi zing gas is the amount of hydrogen contained in the fluidi zing gas in vol . -% .Seite 14 / 40

[0077] P81090WO The method may be designed in such a way, that a temperature of the backflushing gas and / or a temperature of the fluidizing gas introduced in the reducing volume is / are greater than or equal to 300 °C, preferably greater than or equal to 450 °C, preferred greater than or equal to 600 °C . The method may be designed in such a way, that a temperature of the backflushing gas and / or a temperature of the fluidizing gas introduced in the reducing volume is / are lower than or equal to 1100 °C, particularly lower than or equal to 950 °C, preferably lower than or equal to 850 °C, and preferred lower than or equal to 800 °C .

[0078] According to an embodiment of the invention, the method may be designed in such a way, that the backflushing gas and / or the fluidizing gas introduced in the reducing volume is / are at ambient temperature, particularly at around 20 °C .

[0079] The backflushing gas introduced in the reducing volume may comprise hydrogen and / or water vapor and / or Nitrogen. Preferably the backflushing gas consists of hydrogen and water vapor . The backflushing gas may be hydrogen.

[0080] The fluidizing gas introduced in the reducing volume may comprise hydrogen and / and water vapor and / or Nitrogen. Preferably the fluidizing gas consists of hydrogen and water vapor . The fluidizing gas may be hydrogen.

[0081] The method may be designed in such a way, that the discharging gas stream discharged from the reducing volume is at least partially introduced to a reactor volume, particularly to a reactor volume of a direct reduction reactor, preferably a fluidized bed direct reduction reactor, to reduce iron containing particles arranged in the reactor volume to increase a degree of reduction of the iron containing particles in the reactor volume .Seite 15 / 40

[0082] P81090WO The method may be designed in such a way, that the discharging gas stream discharged from the reducing volume is mixed with hydrogen before it is introduced in the reactor volume .

[0083] According to a preferred embodiment, the method may be designed in such a way, that the discharging gas stream discharged from the reducing volume can be added to a reactor inlet gas stream introduced to the reactor volume . According to a preferred embodiment, the method may be designed in such a way, that the discharging gas stream discharged from the reducing volume can be used as a reactor inlet gas stream introduced to the reactor volume .

[0084] The method may be designed in such a way, that at least part of the discharging gas stream discharged from the reducing volume can be added to and / or mixed with the backflushing gas before the backflushing gas is introduced in the reducing volume .

[0085] The method may be designed in such a way, that the discharging gas stream discharged from the reducing volume is mixed with hydrogen before it is added to and / or mixed with the backflushing gas .

[0086] The method may be designed in such a way, that at least part of the discharging gas stream discharged from the reducing volume can be added to and / or mixed with the fluidizing gas before the fluidizing gas is introduced to the reducing volume .

[0087] The method may be designed in such a way, that the discharging gas stream discharged from the reducing volume is mixed with hydrogen before it is added to and / or mixed with the fluidizing gas .Seite 16 / 40

[0088] P81090WO The method may be designed in such a way, that at least part of the discharged iron containing particles from the reducing volume are introduced to a reactor volume of a direct reduction reactor, particularly a fluidized bed direct reduction reactor, to increase a degree of reduction of iron containing particles .

[0089] The method may be designed in such a way, that at least part of the discharged iron containing particles form the reducing volume are introduced to a product stream. The method may be designed in such a way, that at least part of the discharged iron containing particles from the reducing volume are briquetted and / or compacted and / or introduced to a melting furnace, particularly an electric melting furnace, preferably an electric arc furnace or a submerged arc furnace, to be melted. The method may be designed in such a way, that at least part of the discharged iron containing particles form the reducing volume are introduced to a reducing furnace for further processing.

[0090] According to a second aspect of the present invention the problem underlying the present invention is solved by an apparatus for cleaning an introduction gas stream containing iron containing particles, wherein the apparatus comprises a housing limiting a cleaning volume at least partially, wherein the housing comprises an inlet opening and an outlet opening; wherein the inlet opening is configured to introduce the introduction gas stream to the cleaning volume and the outlet opening is configured to discharge a discharging gas stream from the cleaning volume; wherein the housing comprises a particle outlet opening, configured to discharge iron containing particles from the cleaning volume; a filtering device arranged in the cleaning volume of the housing and configured to retain iron containing particles from the introduction gas stream; and wherein the filtering device comprises an average pore size of smaller than or equal to 500 pm, particularly smaller than or equal to 250 pm and preferably smaller than or equal to 100 pm.Seite 17 / 40

[0091] P81090WO

[0092] In the following, the term "intended use" describes the use of the apparatus within a direct reduction plant, preferably as an apparatus for treating an off-gas stream of a direct reduction reactor, particularly a fluidized bed direct reduction reactor .

[0093] In the intended use an apparatus designed in such a way has the advantage that iron containing particles, particularly iron containing particles within an off-gas stream of a direct reduction reactor, can be removed from the off-gas stream, such that the off-gas stream may be recirculated back to the direct reduction reactor for use as a reduction gas . At the same time, the degree of reduction of the iron containing particles retained in the filtering device is increased in the cleaning volume . In this way, the overall yield and efficiency of a direct reduction reactor and / or plant can be increased.

[0094] According to a preferred embodiment, the method according to the first aspect of the invention may use an apparatus according to the second aspect of the invention. Particularly, the method for reducing iron containing particles comprised in an introduction gas stream using an apparatus for cleaning the introduction gas stream, wherein the apparatus comprises a housing limiting a cleaning volume at least partially, wherein the housing comprises an inlet opening and an outlet opening; wherein the inlet opening is configured to introduce the introduction gas stream to the cleaning volume and the outlet opening is configured to discharge a discharging gas stream from the cleaning volume; wherein the housing comprises a particle outlet opening, configured to discharge iron containing particles from the cleaning volume; a filtering device arranged in the cleaning volume of the housing and configured to retain iron containing particles from the introduction gas stream; and wherein the filtering device comprises an average pore size of smaller than or equal toSeite 18 / 40

[0095] P81090WO 500 pm, particularly smaller than or equal to 250 pm and preferably smaller than or equal to 100 pm; comprises the following steps :

[0096] introducing the introduction gas stream to a reducing volume ;

[0097] at least temporarily retaining at least a part of the iron containing particles in the reducing volume; and reducing at least part of the retained iron containing particles increasing their degree of reduction.

[0098] The housing may comprise at least one metal containing material, particularly steel . The cleaning volume may also be referred to as reducing and cleaning volume .

[0099] The filtering device may comprise organic and / or non-organic material, such as a fabric and / or a metal and / or ceramic . The filtering device may comprise a filtration efficiency of smaller than or equal to 10 mg / m3, particularly of smaller than or equal to 5 mg / m3. A filtration efficiency of a filtering device of 10 mg / m3means that one m3of a gas stream under standard temperature and pressure conditions (STP) comprises less than or equal to 10 mg of particles after being filtered with such a filtering device .

[0100] The average pore size of a filtering device determines a minimal average particle size of particles within a gas stream, that can be retained with such a filtering device . A filtering device with an average pore size of equal to 500 pm is capable of retaining particles with an average particle size of 500 pm or greater .

[0101] The filtering device may comprise an average pore size of smaller than or equal to 75 pm, particularly smaller than or equal to 50 pm, preferably smaller than or equal to 25 pm, preferredSeite 19 / 40

[0102] P81090WO smaller than or equal to 15 pm, and particularly preferred smaller than or equal to 10 pm.

[0103] The housing may comprise a backflushing inlet opening, configured to pulsatingly introduce a backflushing gas flow to the cleaning volume .

[0104] In this way, the filtering device can be cleaned of a filter cake, that may form on a filtering surface of the filtering device . In this way, the filtering capacity of the filtering device can be regularly restored throughout a continuous gas cleaning process and the material is brought to the material outlet .

[0105] The filtering device may comprise a filtering surface and a backflushing surface, wherein the filtering device may be arranged in the cleaning volume such that the backflushing surface of the filtering device faces a backflushing outlet opening at least partially.

[0106] A backflushing surface of the filtering device facing a back-flushing outlet opening at least partially means, that the two surfaces may enclose an angle of smaller than 180 ° to each other, particularly smaller than or equal to 90 ° .

[0107] The filtering device may be arranged in the cleaning volume such that the filtering surface of the filtering device faces the inlet opening at least partially.

[0108] The filtering surface and the backflushing surface may be arranged on opposite surfaces of the filtering device .

[0109] The backflushing inlet opening may be fluidly connected to the backflushing outlet opening, particularly via a pipe, a tube, a hose or a similar structure . The backflushing outlet opening maySeite 20 / 40

[0110] P81090WO be arranged in the cleaning volume . The housing may comprise a plurality of backflushing outlet openings . The backflushing inlet opening may be fluidly connected to more than one backflushing outlet opening, particularly to two or more or three or more backflushing outlet openings .

[0111] The inlet opening and the backflushing outlet opening may be arranged such that the filtering device is arranged in between the inlet opening and the backflushing outlet opening. The filtering device may comprise a plurality of filtering units, particularly filtering candles . In the intended use of the apparatus, the introduction gas stream can be continuously cleaned by the filtering device, while the backflushing gas stream can pulsatingly clean one or more than one filtering unit allowing for a continuous filtering process and a simultaneous cleaning of the filtering units .

[0112] The filtering device may be arranged in the cleaning volume such that it separates the cleaning volume in at least two partial volumes, one being an inlet cleaning volume and the other being an outlet cleaning volume; wherein the inlet cleaning volume is in direct fluid connection with the inlet opening and the outlet cleaning volume is in direct fluid connection with the outlet opening; and wherein pores of the filtering device fluidly connect the inlet cleaning volume and the outlet cleaning volume .

[0113] The filtering device may be configured to accumulate the iron containing particles retained from the gas flow, particularly on a filtering surface of the filtering device .

[0114] In the intended use, an average particle size of the retained iron containing particles can be increased through the accumulation, particularly on a filtering surface of the filtering device . In this way, material handling of the accumulated particles can be simplified.Seite 21 / 40

[0115] P81090WO

[0116] The filtering device may be configured to increase an average particles size of the iron containing particles retained from the introduction gas stream.

[0117] The filtering device may be configured to increase a degree of reduction of the iron containing particles retained from the introduction gas stream.

[0118] As the filtering device is configured to retain iron containing particles from the introduction gas stream, those retained particles are kept in the cleaning volume for an increased amount of time . In this way, the retained particles are in contact with the gas inside the cleaning volume for an increased amount of time . As the gas inside the cleaning volume comprises the introduction gas stream, the backflushing gas stream and the fluidizing gas stream, the gas in the cleaning volume has a reduction potential thereby reducing the particles retained in the filtering device .

[0119] The housing may comprise one or more than one fluidizing inlet opening, configured to introduce a fluidizing gas to the cleaning volume .

[0120] In the intended use, introducing fluidizing gas is used to improve material handling of the retained iron containing particles discharged from the cleaning volume . By introducing a fluidizing gas to the cleaning volume clogging of the particle outlet opening for discharging the retained iron containing particles from the cleaning volume can be mitigated.

[0121] One or more than one fluidizing inlet opening may be configured to pulsatingly or continuously introduce a fluidizing gas to the cleaning volume .Seite 22 / 40

[0122] P81090WO The particle outlet opening may be arranged at a bottom part, particularly in a bottom wall of the housing. One or more than one fluidizing inlet opening may be arranged in a wall of the housing, particularly above the particle outlet opening. The inlet opening may be arranged in a wall of the housing, particularly above the one or more than one fluidizing inlet opening. The outlet opening may be arranged in a wall of the housing, particularly above the inlet opening. The backflushing inlet opening may be arranged in a top part of the housing, particularly in a wall of the housing, preferably above the outlet opening .

[0123] According to a preferred embodiment, the housing of the apparatus may comprise a plurality of inlet openings, particularly two or more inlet openings or three or more inlet openings . The housing of the apparatus may comprise a plurality of outlet openings, particularly two or more outlet openings or three or more outlet openings . The housing of the apparatus may comprise a plurality of particle outlet openings, particularly two or more particle outlet openings or three or more particle outlet openings . The housing of the apparatus may comprise a plurality of backflushing inlet openings, particularly two or more backflushing inlet openings or three or more backflushing inlet openings .

[0124] The apparatus may be configured to maintain a cleaning volume temperature of greater than or equal to 300 °C, preferably of greater than or equal to 450 °C, particularly of greater than or equal to 550 °C, preferred of greater than or equal to 600 °C and particularly preferred of greater than or equal to 650 °C .

[0125] The apparatus may be configured to maintain a cleaning volume temperature of lower than or equal to 1100 °C, particularly of lower than or equal to 950 °C, preferably of lower than or equal to 850 °C, and preferred of lower than or equal to 800 °C .Seite 23 / 40

[0126] P81090WO According to a preferred embodiment, the apparatus is configured to maintain a cleaning volume temperature of around 700 °C .

[0127] The cleaning volume temperature is preferably the temperature of the cleaning volume, particularly the temperature of the gas and / or gas composition of the cleaning volume . Particularly, iron containing particles retained in the cleaning volume may comprise a temperature different from the cleaning volume temperature . Alternatively, iron containing particles retained in the cleaning volume may comprise the cleaning volume temperature .

[0128] The apparatus may be configured to maintain a cleaning volume composition with a hydrogen content of greater than or equal to 50 vol . -%, particularly of greater than or equal to 60 vol . -%, preferably of greater than or equal to 70 vol . -%, and particularly preferred of greater than or equal to 75 vol . -% .

[0129] The apparatus may be configured to maintain a cleaning volume composition with a hydrogen content of lower than or equal to 100 vol . -%, particularly of lower than or equal to 90 vol . -%, preferably of lower than or equal to 85 vol . -%, and particularly preferred of lower than or equal to 80 vol . -% .

[0130] According to a preferred embodiment, the apparatus may be configured to maintain a cleaning volume temperature of greater than or equal to 500 °C and lower than or equal to 900 °C and a hydrogen content of the cleaning volume composition of lower than or equal to 80 vol . -% and greater than or equal to 63 vol . -% . It has been found out, that a reduction potential of the cleaning volume with this temperature and hydrogen content is particularly high, such that the iron containing particles retained in the cleaning volume can be reduced to an even higher degree of reduction.Seite 24 / 40

[0131] P81090WO The cleaning volume composition is preferably the gas composition in the cleaning volume . In other words, gas composition specifications in vol . -% typically do not include iron containing particles in the cleaning volume . For example, a cleaning volume composition with a hydrogen content of greater than or equal to 50 vol . -% means, that the gas composition in the cleaning volume has a hydrogen content of greater than or equal to 50 vol . -%, regardless of the amount of iron containing particles retained in the cleaning volume .

[0132] The apparatus may be configured to carry out a method according to the first aspect of the invention. Particularly, the apparatus may comprise a control unit, wherein the control unit is configured to carry out a method according to the first aspect of the invention. The control unit may be any electronic device that is configured to send signals, to receive signals and to process signals and to control at least a part, particularly multiple parts of the apparatus .

[0133] The apparatus may comprise one or more than one measuring device to measure one or more than one process parameter . A process parameter may comprise a temperature, particularly a reducing volume temperature . A process parameter may comprise a pressure, particularly a pressure of the reducing volume, particularly relative to an atmospheric pressure . A process parameter may comprise cleaning and / or reducing volume composition. The control unit may be data-connected to the measuring device . The control unit may be configured to receive one or more than one process parameter from the one or more than one measuring device, process them and act at least indirectly on the apparatus, particularly by changing at least one operating parameter of the apparatus . An operating parameter may be a power of a heating element, particularly a heating element in order to change the reducing volume temperature, particularly to a target reducing volume temperature .Seite 25 / 40

[0134] P81090WO

[0135] According to a third aspect of the present invention, the problem underlying the present invention is further solved by a system comprising an apparatus according the second aspect of the invention and a direct reduction reactor, wherein the direct reduction reactor comprises a reactor housing limiting a reactor volume at least partially, wherein the reactor housing comprises a reactor outlet opening configured to discharge a reactor outlet gas stream from the reactor volume; and wherein the reactor volume is fluidly connected to the cleaning volume via the reactor outlet opening and the inlet opening of the housing of the apparatus .

[0136] A system designed in such a way has the advantage that iron containing particles within the reactor outlet gas stream, can be removed from the reactor outlet gas stream, such that the reactor outlet gas stream may be recirculated back to the reactor volume of the direct reduction reactor for further use as a reduction gas . At the same time, the degree of reduction of the iron containing particles retained in the filtering device of the apparatus is increased in the cleaning volume . In this way, the overall yield and efficiency of the system comprising a direct reduction reactor can be increased.

[0137] The reactor housing may comprise a reactor inlet opening configured to introduce a reactor inlet gas stream to the reactor volume, wherein the reactor volume is fluidly connected to the cleaning volume via the reactor inlet opening and the outlet opening of the housing of the apparatus .

[0138] A system designed in such a way has the advantage that the reactor outlet gas stream, after being cleaned by the apparatus, can be recirculated back to the back to the reactor volume of the direct reduction reactor for further use as a reduction gas resulting in a near full recirculating use of the reduction gas .Seite 26 / 40

[0139] P81090WO

[0140] The reactor housing may comprise a product outlet opening configured to discharge a product stream from the reactor volume of the direct reduction reactor .

[0141] The system may comprise a gas washing device comprising a gas washing volume, wherein the cleaning volume is fluidly connected to the gas washing volume via the outlet opening of the housing of the apparatus and a gas washing inlet opening of the gas washing device . The gas washing volume may be fluidly connected to the reactor volume via a gas washing outlet opening of the gas washing device and a reactor inlet opening. The gas washing device may be arranged between the apparatus and the direct reduction reactor in a flow direction of the discharging gas stream discharged from the cleaning volume of the apparatus . Thus, the cleaning volume may be fluidly connected to the reactor volume via the gas washing volume .

[0142] The system may comprise a de-dusting device, particularly a cyclone, wherein the de-dusting device comprises a de-dusting volume and a de-dusting device outlet opening; and wherein the dedusting volume may be fluidly connected with the cleaning volume via the de-dusting device outlet opening and the inlet opening of the housing of the apparatus . The de-dusting volume may be fluidly connected with the reactor volume via the reactor outlet opening and a de-dusting device inlet opening. The de-dusting device may be arranged between the direct reduction reactor and the apparatus in a flow direction of the reactor outlet gas stream discharged from the reactor volume of the direct reduction reactor . Thus, the reactor volume may be fluidly connected to the cleaning volume via the de-dusting volume . The de-dusting device may comprise a de-dusting device particle outlet opening configured to discharge particles, particularly iron containing particles, separated from a gas stream in the de-dusting device volume .Seite 27 / 40

[0143] P81090WO

[0144] The system may comprise a compressor device configured to generate a gas stream from the cleaning volume of the apparatus to the reactor volume; and / or a heating device configured to heat a gas stream, particularly the reactor inlet gas stream, particularly to a temperature of greater than or equal to 600 °C, particularly of greater than or equal to 800 °C, preferably of greater than or equal to 900 °C, preferred of greater than or equal to 1000 °C and particularly preferred of greater than or equal to 1100 °C . The compressor device and / or the heating device may be arranged between the gas washing device and the direct reduction reactor in a flow direction of the discharging gas stream discharged from the gas washing volume .

[0145] The direct reduction reactor may be a fluidized bed direct reduction reactor . Particularly, the direct reduction reactor may be a bubbling fluidized bed direct reduction reactor .

[0146] The system may comprise a return device configured to introduce iron containing particles discharged from the particle outlet opening of the apparatus and / or discharged from the de-dusting device particle outlet opening to the reactor volume and / or to a product stream. The fluidized bed direct reduction reactor, the de-dusting device and the return device thus may form a circulating fluidized bed direct reduction reactor .

[0147] The system may comprise one or more than one measuring device, particularly arranged in order to measure one or more than one process parameter, particularly one or more than one process parameter of the direct reduction reactor and / or the de-dusting device and / or the gas washing device and / or the compressor device and / or the heating device and / or the return device . The control unit may be configured to receive one or more than one process parameter from the one or more than one measuring device, process them and act at least indirectly on the direct reduction reactorSeite 28 / 40

[0148] P81090WO and / or the de-dusting device and / or the gas washing device and / or the compressor device and / or the heating device and / or the return device, particularly by changing at least one operating parameter of the direct reduction reactor and / or the de-dusting device and / or the gas washing device and / or the compressor device and / or the heating device and / or the return device in order to control a process running on the system.

[0149] According to a fourth aspect of the present invention, the problem underlying the present invention is further solved by a use of an apparatus according to the second aspect of the invention or a system according to the third aspect of the invention for cleaning a gas stream containing iron containing particles and reducing at least part of the iron containing particles .

[0150] It shall be noted, that the advantages of the first aspect of the invention apply to the second aspect, the third aspect and the fourth aspect of the invention and vice versa . Further, the features of the first aspect of the invention may be combined individually and cumulatively with the features of the second aspect and the third aspect of the invention and vice versa . Lastly, the features of the second aspect of the invention may be combined individually and cumulatively with the features of the third aspect of the invention and vice versa .

[0151] Further advantages, details and features of the invention are shown in the following examples . These show in detail :

[0152] Figure 1 : a schematic drawing of an apparatus for cleaning an introduction gas stream according to a first embodiment; and

[0153] Figure 2 : a schematic drawing of a system comprising the apparatus according to the first embodiment .Seite 29 / 40

[0154] P81090WO In the following description, the same reference numerals denote the same components or the same features, so that a description of a component in relation to one figure also applies to the other figures, thus avoiding a repetitive description. Furthermore, individual features described in connection with one embodiment can also be used separately in other embodiments .

[0155] Figure 1 shows a schematic view of an apparatus 10 for cleaning an introduction gas stream 101 containing iron containing particles 105 according to a first embodiment, wherein the apparatus 10 comprises a housing 11 limiting a cleaning volume 20 at least partially, wherein the housing 11 comprises an inlet opening 12 and an outlet opening 13, wherein the inlet opening 12 is configured to introduce the introduction gas stream 101 to the cleaning volume 20 and the outlet opening 13 is configured to discharge a discharging gas stream 102 from the cleaning volume 20, wherein the housing 11 comprises a particle outlet opening 14, configured to discharge iron containing particles 105 from the cleaning volume 20, and a filtering device 15 arranged in the cleaning volume 20 of the housing 11 and configured to retain iron containing particles 105 from the introduction gas stream 101. The filtering device 15 may comprise an average pore size of smaller than or equal to 500 pm.

[0156] The housing 11 further comprises a plurality of backflushing inlet openings 16, wherein each backflushing inlet opening 16 is configured to introduce a backflushing gas 103 to the cleaning volume 20. Each backflushing inlet opening is be fluidly connected to two backflushing outlet openings 161 via a pipe . The backflushing outlet openings 161 are arranged in the cleaning volume 20. The filtering device 15 comprises a filtering surface 18 and a backflushing surface 19, wherein the filtering device 15 is arranged in the cleaning volume 20 such that the back-flushing surface 19 of the filtering device 15 faces at leastSeite 30 / 40

[0157] P81090WO one backflushing outlet opening 161 at least partially. The filtering surface 18 and the backflushing surface 19 are arranged on opposite surfaces of the filtering device 15. Further, the filtering device 15 comprises a plurality of filtering candles .

[0158] The filtering device 15 is arranged in the cleaning volume 20 such that it separates the cleaning volume 20 in at least two partial volumes, one being an inlet cleaning volume 21 and the other being an outlet cleaning volume 22, wherein the inlet cleaning volume 21 is in direct fluid connection with the inlet opening 12 and the outlet cleaning volume 22 is in direct fluid connection with the outlet opening 13, and wherein pores of the filtering device 15 fluidly connect the inlet cleaning volume 21 and the outlet cleaning volume 22.

[0159] The housing 11 comprises more than one fluidizing inlet opening 17, configured to introduce a fluidizing gas 104 to the cleaning volume 20. The particle outlet opening 14 is arranged at a bottom part of the housing 11. The more than one fluidizing inlet opening 17 is arranged in a wall of the housing 11 above the particle outlet opening 14. The inlet opening 12 is arranged in a wall of the housing 11 above the more than one fluidizing inlet opening 17. The outlet opening 13 is arranged in a wall of the housing 11 above the inlet opening 12. The backflushing inlet opening 16 is arranged in a top part of the housing 11 above the outlet opening 13.

[0160] Figure 2 shows a schematic view of a system 100 comprising the apparatus 10 according to the first embodiment and a direct reduction reactor 30. The direct reduction reactor 30 comprises a reactor housing 32 limiting a reactor volume 31 at least partially, wherein the reactor housing 32 comprises a reactor outlet opening 33 configured to discharge a reactor outlet gas stream 107 from the reactor volume 31, wherein the reactor volume 31 is fluidly connected to the cleaning volume 20 via the reactorSeite 31 / 40

[0161] P81090WO outlet opening 33 and the inlet opening 12 of the housing 11 of the apparatus 10.

[0162] The reactor housing 32 further comprises a reactor inlet opening 34 configured to introduce a reactor inlet gas stream 106 to the reactor volume 31, wherein the reactor volume 31 is fluidly connected to the cleaning volume 20 via the reactor inlet opening 34 and the outlet opening 13 of the housing 11 of the apparatus 10. The reactor housing 32 further comprises a product outlet opening 35 configured to discharge a product stream 108 from the reactor volume 31.

[0163] The system 100 further comprises a gas washing device 50 comprising a gas washing volume 51, wherein the cleaning volume 20 is fluidly connected to the gas washing volume 51 via the outlet opening 13 of the housing 11 of the apparatus 10 and a gas washing inlet opening 52 of the gas washing device 50. The gas washing volume 51 further is fluidly connected to the reactor volume 31 via a gas washing outlet 53 opening of the gas washing device 50 and the reactor inlet opening 34. The gas washing device 50 is arranged between the apparatus 10 and the direct reduction reactor 30. Thus, the cleaning volume 20 is fluidly connected to the reactor volume 31 via the gas washing volume 51 .

[0164] The system 100 further comprises a de-dusting device 40, wherein the de-dusting device 40 comprises a de-dusting volume 41 and a de-dusting device outlet opening 43, and wherein the de-dusting volume 41 is fluidly connected with the cleaning volume 20 via the de-dusting device outlet opening 43 and the inlet opening 12 of the housing 11 of the apparatus 10. The de-dusting volume 41 further is fluidly connected with the reactor volume 31 via the reactor outlet opening 33 and a de-dusting device inlet opening 42. The de-dusting device 40 is a cyclone . The de-dusting device 40 is arranged between the direct reduction reactor 30 and theSeite 32 / 40

[0165] P81090WO apparatus 10. Thus the reactor volume 31 is fluidly connected to the cleaning volume 20 via the de-dusting volume 41. The dedusting device 40 further comprises a de-dusting device particle outlet opening 44 configured to discharge particle from the dedusting device volume 41 of the de-dusting device 40.

[0166] The system 100 further comprises a compressor device 60 configured to generate a gas stream 102, 106 from the cleaning volume 20 of the apparatus 10 to the reactor volume 31, and a heating device 70 configured to heat the reactor inlet gas stream 106 to a temperature of greater than or equal to 600 °C . The compressor device 60 and the heating device 70 are arranged between the washing device 50 and the direct reduction reactor 30.

[0167] The system 100 comprises a return device 80 configured to introduce iron containing particles 105 discharged from the particle outlet opening 14 of the apparatus 10 and the de-dusting device particle outlet opening 44 of the de-dusting device 40 to the reactor volume 31. The direct reduction reactor 30 is a fluidized bed direct reduction reactor 30 and together with the de-dusting device 40 and the return device 80 forms a circulating fluidized bed direct reduction reactor 30. The return device 80 is further configured to introduce iron containing particles 105 discharged from the particle outlet opening 14 of the apparatus 10 and the de-dusting device particle outlet opening 44 of the de-dusting device 40 to the product stream 108, particularly the product stream 108 of the direct reduction reactor 30. The iron containing particles 105 discharged from the cleaning and reducing volume 20 of the apparatus 10 may directly be fed to the product stream 108.Seite 33 / 40

[0168] P81090WO Reference numerals

[0169] Apparatus

[0170] Housing

[0171] Inlet opening

[0172] Outlet opening

[0173] Particle outlet opening

[0174] Filtering device

[0175] Backflushing inlet opening

[0176] Backflushing outlet opening

[0177] Fluidizing inlet opening

[0178] Filtering surface (of the filtering device) Backflushing surface (of the filtering device) Cleaning (and reducing) volume

[0179] Inlet cleaning volume

[0180] Outlet cleaning volume

[0181] Direct reduction reactor

[0182] Reactor volume

[0183] Reactor housing

[0184] Reactor outlet opening

[0185] Reactor inlet opening

[0186] Product outlet opening

[0187] De-dusting device

[0188] De-dusting volume

[0189] De-dusting device inlet opening

[0190] De-dusting device outlet opening

[0191] De-dusting device particle outlet opening Gas washing device

[0192] Gas washing volume

[0193] Gas washing inlet opening

[0194] Gas washing outlet opening

[0195] Compressor device

[0196] Heating device

[0197] Return device

[0198] SystemSeite 34 / 40

[0199] P81090WO

[0200] Introduction gas stream Discharging gas stream Backflushing gas Fluidizing gas

[0201] Iron containing particles Reactor inlet gas stream Reactor outlet gas stream Product stream

Claims

Seite 35 / 40P81090WO Claims1. Method for reducing iron containing particles ( 105) comprised in an introduction gas stream ( 101 ) , wherein the method comprises the following steps :introducing the introduction gas stream ( 101 ) to a reducing volume (20) ;at least temporarily retaining at least a part of the iron containing particles ( 105) in the reducing volume (20) ; and reducing at least part of the retained iron containing particles ( 105) increasing their degree of reduction.

2. Method according to claim 1, wherein the method comprises the following step :reducing at least part of the retained iron containing particles ( 105) to a degree of reduction of greater than or equal to 12 %, particularly of greater than or equal to 30 % and preferably of greater than or equal to 50 % .

3. Method according to claim 1 or 2, wherein the method comprises the following steps :discharging a discharging gas stream ( 102 ) from the reducing volume (20) , wherein the discharging gas stream ( 102 ) contains less iron containing particles ( 105) than the introduction gas stream ( 101 ) introduced to the reducing volume (20) ; and / orintroducing a backflushing gas ( 103) to the reducing volume (20) ; and / orpulsatingly or continuously introducing a fluidizing gas ( 104 ) to the reducing volume (20) ; and / ordischarging the retained iron containing particles ( 105) from the reducing volume (20) .

4. Method according to one of the preceding claims, wherein the method comprises a step of increasing an average particleSeite 36 / 40P81090WO si ze of at least a part of the retained iron containing particles ( 105 ) .5 . Method according to one of the preceding claims , wherein a temperature of the introduction gas stream ( 101 ) introduced in the reducing volume ( 20 ) is greater than or equal to 300 ° C, preferably greater than or equal to 450 ° C, preferred greater than or equal to 600 ° C .6 . Apparatus ( 10 ) for cleaning an introduction gas stream ( 101 ) containing iron containing particles ( 105 ) , wherein the apparatus ( 10 ) comprises :a housing ( 11 ) limiting a cleaning volume ( 20 ) at least partially, wherein the housing ( 11 ) comprises an inlet opening ( 12 ) and an outlet opening ( 13 ) ;wherein the inlet opening ( 12 ) is configured to introduce the introduction gas stream ( 101 ) to the cleaning volume ( 20 ) and the outlet opening ( 13 ) is configured to discharge a discharging gas stream ( 102 ) from the cleaning volume ( 20 ) ;wherein the housing ( 11 ) comprises a particle outlet opening ( 14 ) , configured to discharge iron containing particles ( 105 ) from the cleaning volume ( 20 ) ;a filtering device ( 15 ) arranged in the cleaning volume ( 20 ) of the housing ( 11 ) and configured to retain iron containing particles ( 105 ) from the introduction gas stream ( 101 ) ; andwherein the filtering device ( 15 ) comprises an average pore si ze of smaller than or equal to 500 pm, particularly smaller than or equal to 250 pm and preferably smaller than or equal to 100 pm .7 . Apparatus ( 10 ) according to claim 6 , wherein the housing ( 11 ) comprises a backflushing inlet opening ( 16 ) , configured toSeite 37 / 40P81090WO pulsatingly introduce a backflushing gas ( 103 ) to the cleaning volume ( 20 ) .8 . Apparatus ( 10 ) according to claim 7 , whereinthe filtering device ( 15 ) comprises a filtering surface ( 18 ) and a backflushing surface ( 19 ) ; andwherein the filtering device ( 15 ) is arranged in the cleaning volume ( 20 ) such that the backflushing surface ( 19 ) of the filtering device ( 15 ) faces a backflushing outlet opening ( 161 ) at least partially .9 . Apparatus ( 10 ) according to one of the claims 6 to 8 , whereinthe filtering device ( 15 ) is arranged in the cleaning volume ( 20 ) such that it separates the cleaning volume ( 20 ) in at least two partial volumes , one being an inlet cleaning volume ( 21 ) and the other being an outlet cleaning volume ( 22 ) ; wherein the inlet cleaning volume ( 21 ) is in direct fluid connection with the inlet opening ( 12 ) and the outlet cleaning volume ( 22 ) is in direct fluid connection with the outlet opening ( 13 ) ; andwherein pores of the filtering device ( 15 ) fluidly connect the inlet cleaning volume ( 21 ) and the outlet cleaning volume ( 22 ) .10 . Apparatus ( 10 ) according to one of the claims 6 to 9 , wherein the filtering device ( 15 ) is configured to accumulate the iron containing particles ( 105 ) retained from the introduction gas stream ( 101 ) , particularly on a filtering surface ( 18 ) of the filtering device ( 15 ) .11 . Apparatus ( 10 ) according to one of the claims 6 to 10 , wherein the filtering device ( 15 ) is configured to increase a degree of reduction of the iron containing particles ( 105 ) retained from the introduction gas stream ( 101 ) .Seite 38 / 40P81090WO12 . Apparatus ( 10 ) according to one of the claims 6 to 11 , wherein the housing ( 11 ) comprises one or more than one fluidi zing inlet opening ( 17 ) , configured to introduce a fluidi zing gas ( 104 ) to the cleaning volume ( 20 ) .13 . Apparatus ( 10 ) according to one of the claims 6 to 12 , wherein the apparatus ( 10 ) is configured to maintain a cleaning volume temperature of greater than or equal to 300 ° C, preferably of greater than or equal to 450 ° C, particularly of greater than or equal to 550 ° C, preferred of greater than or equal to 600 ° C and particularly preferred of greater than or equal to 650 ° C .14 . Apparatus ( 10 ) according to one of the claims 6 to 13 , wherein the apparatus ( 10 ) is configured to maintain a cleaning volume composition with a hydrogen content of greater than or equal to 50 vol . -% , particularly greater than or equal to 60 vol . -% , preferably greater than or equal to 70 vol . -% , and particularly preferred greater than or equal to 75 vol . -% .15 . Apparatus ( 10 ) according to one of the claims 6 to 14 , wherein the apparatus ( 10 ) is configured to carry out a method according to one of the claims 1 to 5 .16 . System ( 100 ) comprising an apparatus ( 10 ) according to one of the claims 6 to 15 and a direct reduction reactor ( 30 ) , whereinthe direct reduction reactor ( 30 ) comprises a reactor housing ( 32 ) limiting a reactor volume ( 31 ) at least partially, wherein the reactor housing ( 32 ) comprises a reactor outlet opening ( 33 ) configured to discharge a reactor outlet gas stream ( 107 ) from the reactor volume ( 31 ) ; andwherein the reactor volume ( 31 ) is fluidly connected to the cleaning volume ( 20 ) via the reactor outlet opening ( 33 )Seite 39 / 40P81090WO and the inlet opening ( 12 ) of the housing ( 11 ) of the apparatus ( 10 ) .17 . System ( 100 ) according to claim 16 , wherein the reactor housing ( 32 ) comprises a reactor inlet opening ( 34 ) configured to introduce a reactor inlet gas stream ( 106 ) to the reactor volume ( 31 ) , wherein the reactor volume ( 31 ) is fluidly connected to the cleaning volume ( 20 ) via the reactor inlet opening ( 34 ) and the outlet opening ( 13 ) of the housing ( 11 ) of the apparatus ( 10 ) .18 . Use of an apparatus ( 10 ) according to one of the claims 6 to 15 or a system ( 100 ) according to claim 16 or 17 for cleaning a gas stream containing iron containing particles ( 105 ) and reducing at least part of the iron containing particles ( 105 ) .

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