GB2578645A

GB2578645A - Method and apparatus for treating waste material

Info

Publication number: GB2578645A
Application number: GB1817979.6A
Authority: GB
Inventors: Lloyd Owain; Lloyd Jacob
Original assignee: DARLOW LLOYD & SONS Ltd
Current assignee: DARLOW LLOYD & SONS Ltd
Priority date: 2018-11-02
Filing date: 2018-11-02
Publication date: 2020-05-20
Anticipated expiration: 2038-11-02
Also published as: WO2020089650A1; GB201817979D0; GB2578645B

Abstract

A method and apparatus for treating filter cake produced from the pickling of iron or steel by washing it with water to remove a contaminant such as a chloride. Washing is performed at a temperature in the range 35-60 0C in the presence of an oxidizing agent such as air. The washed material can have a flocculating agent added thereto and is separated from the water by centrifuging. The material is then agglomerated to form pellets which can be mixed with pellets of iron ore and charged into a furnace. Also agglomerate comprising pellets formed from particles of contaminant depleted material and a binder, wherein the mean greatest dimension of the pellets lies in the range 10-50 mm, the iron content is at least 45 % by weight, the binder content is no more than 10 % by weight, the contaminant content is no more than 1.0 % by weight, the mean maximum particle dimension is no more than 1.0 mm, the moisture content is no more than 5.0 % by weight, or the content of particles having a greatest dimension of less than 10 mm is no more than 5.0 % by weight.

Description

Method and apparatus for treating waste material BACKGROUND OF THE INVENTION [0001] The present disclosure relates to the processing of waste material comprising iron and contaminant-containing species, such as solid waste derived from steel pickling processes.

[0002] The present invention concerns a method of treating waste material comprising iron and contaminant-containing species, and a material makeable by such methods. The invention also concerns an apparatus for treating such waste material. [0003] The iron and steel industry produces a large volume of waste material, such as so-called filter cakes. The filter cakes are typically produced as a by-product of the pickling process in which acid (typically hydrochloric acid or sulphuric acid, but sometimes phosphoric, nitric or hydrofluoric acid, or a combination of the same) is used to clean the surface of a metal. The liquor remaining typically comprises iron in various oxidation states and acid. The liquid component of the liquor may be used as a cleaning liquid (for example, in sewage treatment works). However, supply far exceeds demand and much of the liquor is mixed with alkali for neutralisation, with the solid component being pressed into so-called filter cakes which are then put into landfill. Such deposition into landfill is wasteful and potentially damaging to the environment.

[0004] The present invention seeks to mitigate the above-mentioned problems.

SUMMARY OF THE INVENTION

[0005] In accordance with a first aspect of the present invention there is provided a method of treating a waste material comprising iron and contaminant-containing species to produce a contaminant-depleted material, the method comprising: contacting with one another the waste material and a solvent capable of removing contaminant-containing species from the waste material.

[0006] The applicant has surprisingly discovered that waste material comprising iron and contaminant-containing species (such as chlorine-containing species found in -2 -pickling process filter cake) may be treated to significantly reduce the amount of contaminant-containing species in the resultant product, thereby making the product suitable for use, for example, in a blast furnace. For the avoidance of doubt, "contaminant-containing species" may refer to one or more such species. For the avoidance of doubt, the present invention relates to the removal of contaminant-containing species from the waste material, for example, treating a waste material comprising iron and chlorine-containing species to produce a chlorine-depleted material.

[0007] The contaminant-containing species optionally comprises one or more of a chlorine-containing species, a sulphur-containing species, a nitrogen-containing species, a phosphorous-containing species, a fluorine-containing species and a citrate-containing species. The contaminant-containing species optionally comprises one or more of a chlorine-containing species or a sulphur-containing species. The contaminant-containing species optionally comprises a chlorine-containing species. The chlorine-containing species optionally comprises chloride ions, but other species arc possible. The contaminant-containing species is optionally capable of being removed by an aqueous solvent. The term "solvent" is used to indicate that it dissolves a contaminant-containing species. Contacting the solvent and waste material with one another produces a contaminant-depleted material. The contaminant-containing species optionally comprises an anion.

[0008] The waste material may comprise, and optionally be, a by-product of a steel making process, such as the pickling of iron or steel. The contaminant-containing species is typically introduced into a waste material by the steel making process, such as the pickling of iron or steel. The waste material may therefore comprise filter cake, optionally filter cake from the pickling of iron or steel.

100091 The method may additionally comprise providing said solvent.

[0010] The solvent optionally comprises water, optionally at least 80wt% water and optionally at least 90wt% water. The solvent is optionally water.

[0011] The weight of the solvent may be up to 80% of the total weight of the solvent and waste material, optionally up to 70%, optionally up to 60% and optionally up to 50% of the total weight of the solvent and waste material. The weight of the solvent may be at least 20% of the total weight of the solvent and waste material, optionally at -3 -least 30%, optionally at least 40% and optionally at least 50% of the total weight of the solvent and waste material. The weight of the solvent may be from 30% to 70% of the total weight of the solvent and waste material, and optionally from 50% to 65% of the total weight of the solvent and waste material. The applicant has surprisingly found that making a slurry with such a composition has proved to be effective.

[0012] The solvent may be at a temperature of at least 10°C. The solvent may optionally be at a temperature of at least 25°C, optionally at least 30°C, optionally at least 35°C, optionally at least 40°C, optionally at least 45°C and optionally at least 50°C. The solvent may be at a temperature of no more than 80°C, optionally at a temperature of no more than 60°C. The solvent which optionally comprises water (optionally at least 80wt% water) may be at a temperature of at least 10°C, optionally be at a temperature of at least 25°C, optionally at least 30°C, optionally at least 35°C, optionally at least 40°C, optionally at least 45°C and optionally at least 50°C. The solvent which optionally comprises water (optionally at least 80wt% water) may be at a temperature of no more than 80°C, optionally at a temperature of no more than 60°C. It has unexpectedly been found that using warm water facilitates the formation of magnetite, a source of iron and a valuable dyestuff [0013] The iron in the waste material may be in any oxidation state but typically the majority of iron is iron (II) or iron (III). The waste material typically comprises both iron (II) and iron (III), for example, comprising a core or inner portion comprising iron (II), and an outer portion comprising iron (III).

[0014] The waste material typically comprises at least 2Owt% iron, optionally at least 30wt.% iron and optionally at least 40wt% iron. The waste material optionally comprises up to 60wt?,10, optionally up to 55wt% iron and optionally up to 50wt% iron. The waste material optionally comprises more than I wt% contaminant-containing species.

[0015] The waste material optionally comprises iron (II) and/or iron (III) hydroxide or oxide. The waste material optionally has a pH of at least 7, optionally more than 7 and optionally at least 8. The waste material is often neutral or slightly alkaline on account of the process used to produce certain useful waste materials.

[0016] The waste material typically comprises filter cake, such as pickling-line or pickling process filter cake. -4 -

[0017] The method may comprise contacting the waste material and an oxidising agent with one another, thereby producing an oxidised material. For the avoidance of doubt, the term "waste material" includes waste material that has been in contact with the solvent. The oxidising agent is provided to oxidise iron (0) or iron (II) to iron (II) and/or iron (III). The oxidising agent may be brought into contact with the waste material after the waste material has been contacted with the solvent so as to remove the contaminant (such as chloride) from the waste material. However, this is not generally preferred. It is generally preferred that the oxidising agent is in contact with the waste material at the same time as the waste material is in contact with the solvent. [0018] The method may comprise contacting the waste material with the solvent in the presence of the oxidising agent. Therefore, removal of the contaminant-containing species and oxidisation of the iron may take place at the same time.

[0019] The oxidising agent typically comprises a gas, such as air, which may be passed into a vessel containing the waste material and the solvent. The air may not only provide an oxidising agent, but may also beneficially agitate the waste material and the liquid. The vessel may be provided with one or more gas inlets for the introduction of a gas (typically air) therethrough. Air may be provided using one or more pumps, for example. At least one of the one or more inlets may typically be provided at the bottom of the vessel. More than one, optionally most and substantially all of the inlets may be provided at the bottom of the vessel. The vessel may be elongate, for example, so that the removal of the contaminant-containing species and the oxidation are a continuous process i.e. the solvent moves continuously through the vessel. The vessel may be configured for a batch process i.e. removal of chloride and oxidation take place in a bath process; once the process is complete, the vessel is discharged.

100201 The method may comprise sensing for oxygen. The method may comprise sensing for oxygen and, based on said sensing, determining whether oxidation is substantially complete. The method may comprise sensing for oxygen above said solvent. The method may comprise sensing for oxygen using an oxygen sensor. It has been discovered that the waste material will typically take-up oxygen from a gas (such as air) in order to oxidise iron (0) and iron (II) to iron (III). The oxygen remaining in such gas after it has passed through the solvent is typically at a lower level than in the -5 -gas which has not been passed through the solvent. Therefore, if the sensed amount of oxygen in the gas is substantially the same as that in the gas which has not passed through the solvent, then this is an indication that substantially all of the iron in the waste material has been oxidised, and therefore that beneficial oxidation is complete. [0021] The method may comprise bringing the waste material into contact with the solvent in said vessel. Alternatively or additionally, the method may comprise bringing the waste material into contact with the solvent upstream of the vessel to form a sluny and providing said vessel with said slurry. For the avoidance of doubt, "bringing into contact" indicates that the various components were not previously in contact, whereas "contacting" indicates that the various components may already be in contact with one another.

[0022] The method may therefore comprise agitating the waste material and/or solvent. This may be performed by the introduction of the oxidising agent. Additional agitation may also be provided, for example, by stirring. Agitation has proved to be effective at breaking down the waste material into smaller parts, thereby increasing surfacc arca cxposcd to the solvent and oxidising agent, if present.

[0023] The contaminant-depleted (and optionally oxidised) material may optionally comprise at least 50wt% iron and optionally no more than 1.0wt% of said contaminant species. The contaminant-depleted (and optionally oxidised) material may comprise at least 55wt% iron and optionally at least 60wt% iron.The method may comprise separating the contaminant-depleted (and optionally oxidised) material from the solvent. This may comprise removing the solvent. Separating the contaminant-depleted (and optionally oxidised) material from the solvent may comprise permitting the contaminant-depleted (and optionally oxidised) material to settle. The separation may therefore take place in a settler, such as a clarifier, for example, a lamella clarifier. Separating the contaminant-depleted (and optionally oxidised) material from the solvent may comprise filtration. The method may therefore comprise moving the contaminant-depleted (and optionally oxidised) material and at least some of the solvent from the vessel to a settler.

[0024] Separating the contaminant-depleted (and optionally oxidised) material from the solvent may comprise adding a flocculating agent; such flocculating agents may help cause the contaminant-depleted (and optionally oxidised) material to float or -6 -sink, depending on the nature of the flocculating agent. Separating the contaminant-depleted (and optionally oxidised) material from the solvent may comprise centrifuging the contaminant-depleted (and optionally oxidised) material. The method may comprise transferring settled contaminant-depleted (and optionally oxidised) material to a centrifuge.

[0025] The method may comprise agglomerating the contaminant-depleted (and optionally oxidised) material, thereby forming an agglomerate composition comprising pellets. The pellets optionally comprise contaminant-depleted (and optionally oxidised) material and a binder. The contaminant-depleted (and optionally oxidised) material is typically substantially dry when it is agglomerated. Agglomeration may be performed using an agglomerater or bailer to form pellets. The mean greatest dimension of the pellets of the agglomerate composition may be at least 2mm, optionally at least 5mm and optionally at least 10mm. The mean greatest dimension may be up to 100mm, optionally up to 80mm, optionally up to 60mm, optionally up to 50mm and optionally up to 40mm. The mean greatest dimension may be from 10mm to 50mm, for example. The pellets of the agglomerate composition may be substantially spherical, in which case the mean diameter of the pellets of the agglomerate composition may be at least 2mm, optionally at least 5mm and optionally at least 10mm. The mean diameter may be up to 100mm, optionally up to 80mm, optionally up to 60mm, optionally up to 50mm and optionally up to 40mm. The mean diameter may be from 10mm to 50mm, for example. Pellets of such size have been found to be advantageous.

[0026] The pellets of the agglomerate composition are optionally sufficiently robust to withstand the processing associated with pelletised materials used in blast furnaces. For example, the pellets of the agglomerate composition are optionally sufficiently robust to withstand transfer to the blast furnace. The pellets are optionally sufficiently robust to allow the material to be added to the blast furnace without significant physical breakdown of the agglomerates. In this connection, the tumbler index of the pellets of the agglomerate composition may be at least 80, as determined using the TATA tumble index test. Additionally or alternatively, the tumbler index of the pellets of the agglomerate composition may be at least 50% as determined under ISO -7 - 3271:1885, optionally at least 60%, optionally at least 70% and optionally at least 80%.

[0027] Agglomerating the contaminant-depleted (and optionally oxidised) material may comprise mixing the contaminant-depleted (and optionally oxidised) material with a binder. The binder may comprise any suitable binder known to those skilled in the art, for example, ordinary Portland cement.

[0028] In accordance with a second aspect of the present invention, there is provided an agglomerate composition makeable in accordance with the method of the first aspect of the present invention. The agglomerate composition in accordance with the second aspect of the present invention may have those properties described above in relation to the method of the first aspect of the invention.

[0029] In accordance with a third aspect of the present invention, there is provided an agglomerate composition comprising pellets comprising particles of contaminant-depleted (and optionally oxidised) material and a binder, the agglomerate composition optionally comprising one or more of the following optional features: the mean greatest dimension of the pellets of the agglomerate composition is 10-50mm, the iron content of the agglomerate composition is at least 45wt% iron, the binder content is no more than l Owt%, the contaminant content (optionally chloride content) is no more than 1.0wt%, the mean maximum dimension of the particles of contaminant-depleted (and optionally oxidised) material is no more than 1.0mm, the moisture contact of the agglomerate composition is no more than 5.0wt% and the content of the agglomerate composition having a greatest dimension of less than 10mm is no more than 5.0wflib. [0030] In accordance with a fourth aspect of the present invention, there is provided an apparatus for processing a waste material comprising iron and contaminant-containing species, the apparatus comprising: one or more oxidation vessels for containing the waste material and a solvent, the vessel comprising one or more gas inlets for the introduction of oxidising gas (e.g. air) therethrough; a separator configured to receive oxidised material from the one or more oxidation vessels and to separate the oxidised material from the solvent; and -8 -an agglomerator configured to agglomerate material received from the separator.

[0031] Embodiments of the apparatus of the present invention provide a simple and effective way of producing waste which may have sufficiently low levels of contaminant (particularly anionic contaminants, such as chloride) to permit use in a blast furnace. The one or more oxidation vessels facilitate the simultaneous removal of contaminant from the waste material and oxidation of iron in the filter cake to form oxidised material. The agglomerator forms agglomerates, typically in the form of pellets (having a size typically of the order of 10mm) from the oxidised material made in the oxidation vessel(s).

[0032] The apparatus may comprise a sorter upstream of the oxidation vessel(s) for removing oversize particulate.

[0033] The apparatus may comprise a mixer for mixing solvent with the waste material upstream of the oxidation vessel(s).

[0034] The sorter and mixer may be provided by a washer, such as a trommel washer. [0035] One or more, and optionally each. of the oxidation vessels may be a batch processing vessel. Alternatively or additionally, one or more of the oxidation vessels may be a continuous processing vessel. Such continuous processing vessels are typically elongate.

[0036] The apparatus may comprise one or more holding vessels downstream of the oxidation vessel(s) and upstream of the separator. Such holding tanks facilitate the control of fluid flow to the separator.

[0037] The separator may comprise a settler, such as a clarifier, for example, a lamella clarifier. The oxidised material typically settles to the lower portion of the settler. Solvent may be removed from the upper portion of the settler.

[0038] The separator may comprise a centrifuge. A centrifuge is an effective means for drying the oxidised material. If the separator comprises a settler and a centrifuge, then it is preferred that the centrifuge is downstream of the settler and is configured to receive oxidised material and solvent from the settler, optionally in the form of a thickened sludge. -9 -

[0039] The agglomerator may comprise a vacuum extruder or bailer, for example. The agglomerator may be configured to produce agglomerate having a mean greatest dimension of from 10-50mm, for example.

[0040] The apparatus of the fourth aspect of the present invention may be used to perform the method of the first aspect of the present invention. Conversely, the method of the first aspect of the present invention may be performed using the apparatus of the fourth aspect of the present invention.

[0041] The apparatus may comprise an oxygen sensor associated with one of the oxidation vessels. The apparatus may comprise more than one oxygen sensor, each associated with an oxidation vessel. One or more of the oxygen sensors may be configured to control introduction of oxidising agent into one or more of the oxidation vessels. For example, one or more oxygen sensors may be configured to control a gas pump or valve thereby controlling introduction of oxidising agent into one or more of the oxidation vessels.

[0042] In accordance with a fifth aspect of the present invention, there is provided a furnace charge comprising the agglomerate composition in accordance with the second and/or third aspects of the present invention. The furnace charge optionally comprises iron ore, optionally in the form of pellets. The furnace charge optionally comprises iron ore pellets admixed with an agglomerate composition in accordance with the second and/or third aspects of the present invention. The furnace charge is optionally suitable for a blast furnace, and may comprise features which are characteristic of a charge for a blast furnace.

[0043] In accordance with a sixth aspect of the present invention, there is provided a method of charging a furnace, the method comprising providing to the furnace an agglomerate composition in accordance with the second and/or third aspects of the present invention. The furnace is typically a blast furnace.

[0044] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

-10 -

DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: [0046] Figure 1 shows a schematic representation of a method of treating waste material according to a first embodiment of the invention; and [0047] Figure 2 shows a schematic representation of an apparatus for treating waste material according to a second embodiment of the invention.

DETAILED DESCRIPTION

[0048] "Pickling" is a well-known technique in the steel industry. Typically, hydrochloric acid is used to clean the surface of steel (although other acids may be used, such as sulphuric, hydrofluoric, phosphoric, nitric and citric acid, or mixtures of one or more of the same). Pickling with hydrochloric acid produces ferrous chloride, with some residual hydrochloric acid. This waste liquid is then treated with an aqueous suspension of calcium hydroxide, forming a dark blue-green precipitate (believed to be ferrous hydroxide) in an excess of a liquid, typically an alkaline aqueous solution having a pH of about 7-9. Filter pressing is used to remove most of the liquid, forming so-called a solid dark blue-green "filter cake", the surface of which rapidly turns orange-brown. The filter cake is then dumped in landfill.

[0049] The applicant has surprisingly found that if the filter cake containing a chloride-containing species is made into a wet slurry, then the chloride ion levels in the resulting product may be made sufficiently low to use the product in a blast furnace. Furthermore, aeration of the slurry causes oxidation of the iron, which may be beneficial for use in a blast furnace. A method according to an embodiment of the invention will now be described with reference to Figure 1.

[0050] Briefly, the method 100 according to an embodiment of the invention comprises mixing 101 the filter cake and water, contacting 102 the filter cake and water (thereby facilitating removal of the contaminant-containing species (in this example, chloride) from the filter cake) and, at the same time, contacting 103 waste material with an oxidising agent and separating 104 the water and oxidised material from one another.

[0051] In a first experiment, the filter cake and tap water were mixed in a weight ratio of 40:60 in a large bucket to form a very wet slurry. The dry filter cake comprised iron oxides, hydroxides and chloride hydroxides, with some calcium chloride. Oxidising agent (in the form of air) was pumped using fish tank pumps into the bottom of the bucket through air inlets. The slurry was initially green-blue, but turned orange-brown after an hour or so. The oxidation process was monitored by providing an oxygen sensor above the wet slurry, with air being supplied until the oxygen levels sensed were the same as in air, indicating that the slurry was taking-up no more oxygen from the air, indicating that oxidation was complete. Water was removed from the bucket, and the resulting orange-brown powder was filtered and dried. The colour of the powder indicates that most of the iron is iron (Ill). Elemental analysis showed that the chloride level was sufficiently low for the product to be used in a blast furnace. Analysis suggests that the resultant solid material comprises iron III hydroxide and an iron oxide hydroxide. Furthermore, removal of chloride ions has the benefit of increasing the % weight of iron in the product.

[0052] In a sccond cxperimcnt, the first cxperimcnt was repeated, but using warm water at a temperature of about 45°C. Somewhat surprisingly, the product was a black powder, not an orange-brown powder. Analysis of the powder determined that it was magnetite, a source of iron and valuable dyestuff.

[0053] The contaminant-depleted and oxidised powders produced in the first and second experiments above may be agglomerated to produce embodiments of agglomerate composition in accordance with the second and third aspects of the present invention. In this connection, the powders may be admixed with a binder and other additives to facilitate agglomeration. Typical binders include ordinary Portland cement. Those agglomerate compositions may be used in an embodiment of a blast furnace charge in accordance with the fifth aspect of the present invention, and in an embodiment of a method of charging a blast furnace in accordance with the sixth aspect of the present invention.

[0054] A method according to an embodiment of the invention and an apparatus according to a further embodiment of the invention will now be described with reference to Figures 1 and 2. The method is denoted generally by reference numeral 100 and the apparatus is denoted generally by reference numeral 1000. Water and -12 -filter cake are mixed 101 using a trommel wash 1001. The trommel wash 1001 facilitates removal of oversized pieces of waste/rubbish and mixing of the filter cake and water. The ratio of water to filter cake is about 60:40. The trommel wash 1001 feeds mixed water and filter cake into a plurality of batch aeration vessels 1002. In these vessels 1002, the water and filter cake are contacted 102 with one another to facilitate removal of contaminant (in this case, chloride) from the filter cake. Each aeration vessel 1002 comprises a blower 1012 for introducing air into the aeration vessel 1002, thereby facilitating contact 103 between the waste material and an oxidising agent (air). It is thought that the flow of air agitates the content of the aeration vessels 1002, which causes beneficial mixing and also facilitates breakdown of the waste material, facilitating greater contact between the waste material and the water, and therefore faster removal of chloride. Oxygen levels were monitored in the space above the wet slurry to determine whether or not the oxidation process was complete. Oxidation was deemed to be complete when the oxygen level above the slurry was that of normal air. On completion of oxidation, oxidised material and water may be released from each aeration vessel 1002. In this connection, each batch aeration vessel 1002 is provided with a valve 1013 to control release of the contents of the vessel 1002 to a buffer tank 1003. A flocculating agent is introduced via floc inlet 1014 upstream of the buffer tank 1003. The buffer tank 1003 enables storage of water and oxidised material, controlling receipt of the same from the aeration vessels 1002 and controlling release of the same to the downstream separator 1004. The separator 1004 comprises a settler 1004a and a centrifuge 1004b. Water and oxidised material are released from the buffer tank 1003 to the upper portion of the settler 1004a (in the form of a lamella clarifier). The oxidised material settles 104a to the lower portion of the settler 1004a. Water is fed from the upper portion of the settler 1004a to a water buffer tank 1007 for re-use in the trommel wash 1001. The thick sludge which forms in the lower portion of the settler 1004a is fed to the centrifuge 1004b. The centrifuge process 104b removes further water from the sludge, producing oxidised material which is essentially dry. The output of the centrifuge 1004b is fed to an agglomerator 1005 which agglomerates 105 the oxidised material. Binder and additional additives are added 105a to the oxidised material and the mixture is balled 105b. The -13 -agglomerated material is then cured 106 in a curer 1006, ready for use in a blast furnace.

[0055] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described. [0056] The examples above describe methods and an apparatus for removing chloride from waste material. Those skilled in the art will realise that other chlorine-containing contaminant may be removed. Furthermore, those skilled in the art will realise that the method and apparatus may be used to remove different contaminant-containing species, such as sulphur-containing species, fluorine-containing species, nitrogen-containing species, phosphorous-containing species and/or citrate-containing species. [0057] Those skilled in the art will realise that the waste material used in the method of the present invention may be different from that described above.

[0058] Whilst oxidation of the waste material is highly desirable, it is not essential for the method of the present invention in which removal of chloride ions is key.

[0059] The embodiments of the apparatus and method above describe the use of batch oxidation vessels. Those skilled in the art will realise that a continuous process may be used.

[0060] The characteristics of the agglomerated material made by the method of the present invention may be different from that mentioned above. For example, the material may comprise a different iron content, and may be provided in different size or shape.

[0061] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst -14 -of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

-15 -CLAIMS1 A method of treating a waste material comprising iron and contaminant-containing species to produce a contaminant-depleted material, the method comprising: contacting with one another the waste material and a solvent capable of removing contaminant-containing species from the waste material.
2. A method according to claim 1 wherein the waste material comprises a byproduct of a steel making process.
3. A method according to claim 2 wherein the waste material comprises filter cake produced from the pickling of iron or steel.
4. A method according to any preceding claim wherein the contaminant-containing species comprises one or more of a chlorine-containing species, a sulphur-containing species, a nitrogen-containing species, a phosphorous-containing species, a fluorine-containing species and a citrate-containing species
5. A method according to any preceding claim wherein the solvent comprises at least 80% water.
6. A method according to any preceding claim wherein the weight of the solvent is 30% to 70% of the total weight of the solvent and waste material.
7. A method according to any preceding claim wherein the solvent is at a temperature of at least 35°C and no more than 60°C.
8. A method according to any preceding claim comprising contacting the waste material and an oxidising agent with one another, thereby producing a contaminant-depleted and oxidised material.
9. A method according to claim 8 comprising contacting the waste material with the solvent in the presence of the oxidising agent.
10. A method according to claim 8 or claim 9 wherein the oxidising agent comprises oxygen-containing gas (e.g. air).
11. A method according to any of any preceding claim comprising separating the contaminant-depleted (and optionally oxidised) material from the solvent.-16 -
12. A method according to claim 11 wherein separating the contaminant-depleted (and optionally oxidised) material from the solvent comprises permitting the contaminant-depleted (and optionally oxidised) material to settle.
13. A method according to claim 12 comprising adding a flocculating agent.
14. A method according to any claims 11 to 13 wherein separating the oxidised material from the solvent comprises centrifuging the contaminant-depleted (and optionally oxidised) material.
15. A method according to any preceding claim comprising agglomerating the contaminant-depleted (and optionally oxidised material), thereby forming an agglomerate composition comprising pellets.
16. A method according to claim 15 wherein the mean greatest dimension of the pellets of the agglomerate composition is from 10mm to 50mm.
17. An agglomerate composition makeable in accordance with either claim 15 or claim 16 when dependent on any of claims 8 to 10.
18. An agglomerate composition comprising pellets comprising particles of contaminant-dcplctcd (and optionally oxidiscd) material and a binder, the agglomerate composition comprising one or more of the following optional features: the mean greatest dimension of the pellets of the agglomerate composition being 10-50mm, the iron content of the agglomerate being at least 45wt% iron, the binder content being no more than lOwt910, the contaminant content (optionally chloride content) being no more than 1.0wt9i, the mean maximum dimension of the particles of contaminant-depleted (and optionally oxidised) material being no more than 1.0mm, the moisture contact of the agglomerate being no more than 5.0wt% and the content of particles or pellets having a greatest dimension of less than 10mm is no more than 5.0wt?'"o. .
19. A furnace charge comprising an agglomerate composition in accordance with claim 17 or claim 18 and iron ore pellets.
20. A method of charging a furnace, the method comprising providing to the furnace an agglomerate composition in accordance with claim 17 or claim 18.
21. An apparatus for processing a waste material comprising iron and a contaminant-containing species, the apparatus comprising: -17 -one or more oxidation vessels for containing the waste material and a solvent, the vessel comprising one or more gas inlets for the introduction of oxidising gas (e.g. air) therethrough; a separator configured to receive oxidised material from the one or more oxidation vessels and to separate the oxidised material from the solvent; and an agglomerator configured to agglomerate material received from the separator.
22. An apparatus according to claim 21 comprising a trommel washer upstream of the one or more oxidation vessels.
23. An apparatus according to claim 21 or claim 22 comprising one or more holding vessels downstream of the oxidation vessel(s) and upstream of the separator.
24. An apparatus according to any of claims 21 to 23 wherein the separator comprises a settler.
25. An apparatus according to claim 24 wherein the separator comprises a centrifuge downstream of the settler, and which is configured to receive oxidised material and solvent from the settler.