GB2575875A

GB2575875A - Sinter for use in iron-making and/or steel-making

Info

Publication number: GB2575875A
Application number: GB1812307.5A
Authority: GB
Inventors: Graves Daran; Raeburn Mark; Julian Sims Christopher
Original assignee: British Steel PLC
Current assignee: British Steel PLC
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2020-01-29
Also published as: GB201812307D0

Abstract

A method of making particles which can then be sintered and used to make iron or steel by collecting dust particles discharged from iron-making and/or steel making and washing them in water which comprises 2.5-25 % by weight of the particles, whereby the chloride content of the particles is reduced from 0.06-0.5 % by weight to 0.0005-0.06 % by weight. Figure 2 shows apparatus for this method where particles P are fed onto a screen 230 in a rinsing tank 270. Oversize particles F1 (size greater than 5mm) are screened out and pumped as a suspension to a hydro-cyclone 310 which rejects undersized particles (size less than 0.032 mm), with the rest of the particles being fed onto a vibrating dewatering screen 320 where they are dried. The dried particles Pout can then be used to make sinter.

Description

Sinter for use in iron-making and/or steel-making

Field

The present invention relates to sinter for iron-making and/or steel-making processes.

Background to the invention

Generally, iron-making and/or steel-making processes, for example Blast Furnace (BF) processes, Electric Arc Furnace (EAF) processes and the Basic Oxygen Steelmaking (BOS) processes, discharge large amounts of waste products. Similarly, sinter-making processes discharge large amounts of waste products. These waste products include ferrous material and carbon material, which may be collected as particles (also known as particulates, particulate matter (PM) or flue dust) during cleaning and filtering of off gases (also known as flue gases) from these processes.

Historically, these waste products were disposed of in landfills. However, environmental regulations may now prohibit or penalise such disposal. Further, increased environmental regulations may now also consider prohibit or penalise accumulation of these waste products on site. In addition, emission limit values (ELVs) of pollutants, for example PMs and toxic compounds, released to the atmosphere are anticipated to be reduced from 40 mg/Nm for solids and 0.4ng l-TEQ/Nm for dioxins (Nm : normalized cubic metre for standard temperature and pressure; l-TEQ: International Toxic Equivalent).

Hence, improved collection and/or recycling of these waste products (also known as reverts or secondary materials) may be required, to meet environmental regulations. Such recycling may also recover at least some of the Fe and C included in these waste products.

These waste products are typically particles (including particulates thereof) and often fine grained such that these waste products cannot be used directly in iron-making and/or steelmaking processes. Hence, these waste products are typically formed into sinter, by sintermaking, and/or agglomerates, such as briquettes or pellets. The sinter and/or agglomerates may be subsequently included in charges, typically comprising coke, iron ore and/or limestone, for iron-making and/or steel-making processes. By recycling these waste products in this way, at least some of the Fe and C included therein may be recovered while amounts of waste products for disposal may be reduced.

However, in addition Fe and C, these waste products may also include undesirable elements, for example non-metallic elements such as halogens (F, Cl, Br and/or I), N, P and S.

Generally, these undesirable elements and/or compounds thereof may be detrimental to, and/or adversely affect efficiencies of, the sinter-making, iron-making and/or steel-making processes and/or comprise impurities in steel or iron.

Hence, there is a need to improve collection and/or recycling of waste products from ironmaking and/or steel-making processes.

Summary of the Invention

It is one aim of the present invention, amongst others, to provide a method of providing particles for making a sinter for use in iron-making and/or steel-making which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere. For instance, it is an aim of embodiments of the invention to provide a method of providing a sinter for recycling waste products, thereby recovering Fe therefrom, that reduces amounts of undesirable elements therein. For instance, it is an aim of embodiments of the invention to provide a method of iron-making and/or steel-making having an increased efficiency. For instance, it is an aim of embodiments of the invention to provide a method of iron-making and/or steel-making providing an enhanced efficiency of collection of particles discharged therefrom.

A first aspect provides an apparatus for providing particles for making a sinter for use in ironmaking and/or steel-making, the apparatus comprising:

a treating means for treating the particles, including a ferrous material and/or a carbon material, discharged from iron-making and/or steel-making; and a recovering means for recovering the treated particles;

wherein treating the particles comprises removing at least some Cl therefrom by washing in a first aqueous suspension thereof, comprising the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension.

A second aspect provides a method of providing particles for making a sinter for use in ironmaking and/or steel-making, the method comprising:

collecting the particles, including a ferrous material and/or a carbon material, discharged from iron-making and/or steel-making;

treating the collected particles; and recovering the treated particles;

wherein treating the particles comprises removing at least some Cl therefrom by washing in a first aqueous suspension thereof, comprising the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension;

wherein the particles before treating have a first composition comprising:

Cl in a first amount in a range from 0.06 wt.% to 0.5 wt.%, preferably in a range from 0.07 wt.% to 0.4 wt.%, more preferably in a range from 0.08 wt.% to 0.3 wt.% by weight of the particles; wherein the particles after treating have a second composition comprising:

Cl in a second amount in a range from 0.0005 wt.% to 0.06 wt.%, preferably in a range from 0.001 wt.% to 0.05 wt.%, more preferably in a range from 0.01 wt.% to 0.04 wt.% by weight of the particles;

wherein the second amount of Cl is less than the first amount of Cl.

A third aspect provides a method of making a sinter for use in iron-making and/or steelmaking, the method comprising:

providing a feed-sinter by binding iron ore fines, coke fines, flux fines and particles discharged from iron-making and/or steel-making, using a binder; and heating the feed-sinter to make the sinter and thereby discharging particles, including a ferrous material and/or a carbon material;

wherein the method comprises providing the particles according to the second aspect.

A fourth aspect provides a method of iron-making and/or steel-making, comprising:

preparing a charge comprising coke, iron ore, limestone, sinter and optionally, an agglomerate for example a pellet or a briquette; and heating the charge to make iron or steel and thereby discharging particles, including a ferrous material and/or a carbon material;

wherein the method comprises making the sinter according to the third aspect.

A fifth aspect provides particles for use in making a sinter for iron-making and/or steel-making, wherein the particles have a mean size D50 in a range from 0.001 mm to 5 mm, preferably in a range from 0.032 mm to 3.35 mm, more preferably in a range from 0.063 mm to 2 mm, most preferably in a range from 0.125 mm to 1 mm;

optionally wherein the particles have a D90 at most 5 mm, preferably at most 3.35 mm, more preferably at most 2 mm;

optionally wherein the particles have a D10 of at least 0.001 mm, preferably at least 0.032 mm, more preferably at least 0.063 mm;

wherein the particles have a composition comprising:

Fe in a range from 10 wt.% to 60 wt.%, preferably in a range from 15 wt.% to 50 wt.%, more preferably in a range from 20 wt.% to 40 wt.% by weight of the particles;

C in a range from 5 wt.% to 70 wt.%, preferably in a range from 25 wt.% to 60 wt.%, more preferably in a range from 30 wt.% to 50 wt.% by weight of the particles; and

Cl in a range from 0.0005 wt.% to 0.06 wt.%, preferably in a range from 0.001 wt.% to 0.05 wt.%, more preferably in a range from 0.01 wt.% to 0.04 wt.% by weight of the particles.

Detailed Description of the Invention

According to the present invention there is provided a method of providing particles for making a sinter for use in iron-making and/or steel-making, as set forth in the appended claims. Also provided is a method of making a sinter for use in iron-making and/or steel-making, a method of iron-making and/or steel-making and particles for use in making a sinter. Other features of the invention will be apparent from the dependent claims, and the description that follows.

Apparatus for providing particles

The first aspect provides an apparatus for providing particles for making a sinter for use in ironmaking and/or steel-making, the apparatus comprising:

In this way, at least some Cl is removed from the particles by washing in water (i.e. the first aqueous suspension) such that the recovered, treated particles have a relatively lower amount of Cl, as described below in more detail with respect to the second aspect. In this way, sinter made from the treated particles includes a reduced amount of Cl compared with the untreated particles. In turn, an amount of Cl included in the sinter-making and/or the iron-making and/or steel-making is reduced. Hence, deleterious effects due, at least in part, to Cl on the sintermaking and/or the iron-making and/or steel-making are attenuated. Furthermore, the inventors have determined that an amount of Cl included in particles discharged by the sinter-making using the treated particles and/or the iron-making and/or steel-making, made using sinter including the treated particles, is also reduced, as described below in more detail. By reducing the amount of Cl included in the particles discharged by the sinter-making, the iron-making and/or the steel-making, an efficiency of collection thereof by electrostatic precipitation (ESP) is improved. In this way, emissions of particulates from the sinter-making, the iron-making and/or the steel-making to the atmosphere are lowered, since the efficiency of collection of the particles discharged therefrom is improved.

The particles, the sinter, the iron-making, the steel-making, the ferrous material and/or the carbon material may be as described below with respect to the second, third, fourth and/or fifth aspects.

The apparatus comprises a treating means for treating the particles wherein treating the particles comprises removing at least some Cl therefrom by washing in the first aqueous suspension thereof, comprising the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension.

In other words, the particles are washed in water. It should be understood that the washing is low-pressure washing of the particles, for example substantially at atmospheric pressure, rather than high-pressure washing of the particles, for example using a pressurized water sprayer to spray water at high-pressure (for example, at least 50 bar, at least 75 bar, at least 100 bar or at least 125 bar) thereupon. Surprisingly, the inventors have determined that such low-pressure washing is effective in removing Cl, present as soluble salts, from the particles. Furthermore, such low-pressure washing may also be effective in removing other undesirable elements, present as soluble salts, for example. Furthermore, such low-pressure washing reduces cost and/or complexity of a suitable apparatus while also being suitable for relatively high rates of treating, such as required for treating particles discharged from iron-making or steel making.

It should be understood that the first aqueous suspension may include at least some of the particles suspended, dispersed and/or dissolved therein. That is, at least some of the particles and/or parts thereof may dissolve (i.e. be soluble) in the water. It should be understood that, depending at least in part on the amount and/or a type of the particles in the first aqueous suspension, the first aqueous suspension may be known as a slurry. It should be understood that the recovered, treated particles comprise, substantially comprise (i.e. at least 50 wt.% by weight of the particles), essentially comprise (i.e. at least 90 wt.%, preferably at least 95 wt.%, more preferably at least 99 wt.% by weight of the particles) or consist of insoluble particles.

Treating means

In one example, the treating means comprises a tank (also known as a trough or a bath) for washing the particles therein. In one example, the treating means comprises a conveying means, for example a conveyor belt and/or an Archimedes screw, arranged to convey the particles into the tank, for example at a predetermined (i.e. controlled and/or controllable) feed rate, via an open side thereof, for example. In one example, the predetermined feed rate is in a range from 250 kg per hour to 2500 tonnes per hour, preferably in a range from 1 tonne per hour to 250 tonnes per hour, more preferably in a range from 25 tonnes per hour to 100 tonnes per hour, most preferably in a range from 25 tonnes per hour to 75 tonnes per hour, for example 35 tonnes per hour or 50 tonnes per hour. In one example, the treating means comprises a water supply means arranged to supply water, for example into the tank via an inlet thereof, for example at a predetermined (i.e. controlled and/or controllable) flow rate and/or a predetermined (i.e. controlled and/or controllable) pressure. In one example, the predetermined flow rate is in a range from 2.5 m per hour to 25,000 tonnes per hour, preferably in a range from 10 m per hour to 2,500 m per hour, more preferably in a range

3 3 from 100 m per hour to 1000 m per hour, most preferably in a range from 150 m per hour to 750 m per hour, for example 180 m per hour, 350 m per hour or 500 m per hour. In one example, the predetermined pressure is in a range from 0.01 bar to 20 bar, preferably in a range from 0.1 bar to 10 bar, more preferably in a range from 1 bar to 10 bar, for example 5 bar, most preferably in a range from 1.5 to 3 bar. In one example, the water supply means comprises a first pump arranged to pump the water into the tank at the predetermined flow rate and/or the predetermined pressure. In one example, the treating means comprises a discharge means arranged to discharge the first aqueous suspension from the tank via an outlet thereof, for example in or proximal a base thereof. In one example, the discharge means comprises a second pump arranged to pump the first aqueous suspension from the tank at a discharge rate corresponding to a total of the feed rate and the flow rate. In one example, the washing is performed by flowing the first aqueous suspension in and/or through a tank.

The first aqueous suspension comprises the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension. The inventors have determined that these ranges are effective in removing Cl from the particles while enabling relatively high rates of treating and/or enabling pumping of the first aqueous suspension.

Pre-soaking

In one example, the treating means comprises a pre-soaking means arranged to pre-soak the particles before washing, for example by rinsing or showering the particles (i.e. low-pressure spraying) with water.

In this way, subsequent handling of the pre-soaked particles is facilitated and/or loss of dry particles, for example due to wind, is reduced.

First fraction

In one example, the treating means comprises a first fraction rejection means arranged to reject a first fraction of the particles having a size of at least 5 mm, preferably at least 3.35 mm, more preferably at least 2 mm.

That is, relatively larger particles (i.e. the first fraction) are separated from the remainder of the particles, preferably before washing. Such larger particles may not be suitable for sinter making, for example due to size, type and/or composition.

In one example, first fraction rejection means comprises a screen (also known as a mechanical screen or a sieve) arranged to screen the particles, for example received from the conveying means before and/or afer pre-soaking, using a screen having correspondingly-sized perforations therethrough (i.e. 5 mm, 3.35 mm or 2 mm), for example a vibrating screen. In one example, the screen comprises a mesh screen, a perforated screen and/or a wire screen.

Recovering means

The apparatus comprises the recovering means for recovering the treated particles.

In one example, the recovering means comprises a clarifier, for example a pond, a lamellar clarifier, an inclined plate clarifier or a tubular clarifier, arranged to separate the treated particles from the water of the first aqueous suspension, for example received from the treating means via the discharge means.

In one example, the recovering means comprises a hydrocyclone arranged to separate the treated particles from water of the first aqueous suspension, for example received from the treating means via the discharge means. Hydrocyclones are preferred.

The hydrocyclone is able to separate the treated particles from the water due to differences in respective densitites. The first aqueous suspension is fed into the hydrocyclone slightly off centre, causing the feed first aqueous suspension to come into contact with a wall of the hydrocyclone and hence move in a circular path. As the first aqueous suspension is pushed further down by the continuous feed, the solid particles within the hydrocyclone are subjected to a centripetal force. This centripetal force depends, at least in part, upon the particle diameter and compound density such that larger particles are pushed towards a periphery of the hydrocyclone and forced out in an underflow. Most of the clarified water and residual smaller particles (which are subject to a smaller centripetal force) will move towards a core of the hydrocyclone, which is at a slightly lower pressure, causing the clarified water and the residual small particles to flow upwards out of an overflow of the hydrocyclone.

Without wishing to be bound by any theory, it is understood that turbulence in the first aqueous suspension, for example due to pumping and/or moving in the hydrocyclone, where high levels of shear occur, may increase an amount and/or a rate of Cl removal from the particles.

Second fraction

In one example, the recovering means is arranged to reject a second fraction of the particles having a size of at most 0.125 mm, preferably at most 0.063 mm, more preferably at most 0.032 mm.

That is, relatively smaller particles (i.e. the second fraction) are separated from the remainder of the particles. Such smaller particles (also known as super fines) may not be suitable for sinter making, for example due to size, type and/or composition.

In one example, the recovering means comprises a hydrocyclone arranged to reject the second fraction, wherein the second fraction of the particles is included in an overflow thereof and the remainder of the particles is included in an underflow thereof.

In one example, the recovering means, for example a hydrocyclone, is arranged to reject at most 10 wt.%, preferably at most 7 wt.%, more preferably at most 5 wt.%, most preferably at most 4 wt.% by weight of the particles as a second fraction. If the second fraction is too large, fine particles result in blockages and/or pumping failures within the apparatus while reducing an efficiency of recycling of the particles. However, in order to reduce the second fraction, a higher flow rate of the first aqueous suspension into the hydrocyclone is required.

In one example, the recovery means is arranged to recover the second fraction of the particles. In this way, the second fraction of the particles may be extracted from the water, enabling recirculation thereof.

Drying means

In one example, the recovering means comprises a drying means, arranged remove at least some of moisture from the recovered particles. In this way, a Cl content of the recovered particles may be further reduced, since the moisture may include Cl. Hence, by removing the moisture by drying, the Cl content of the recovered particles may be reduced. In one example, the drying means comprises a screen (also known as a mechanical screen or a sieve) having relatively fine perforations therethrough, for example perforations having a size of at most 0.125 mm, preferably at most 0.063 mm, more preferably at most 0.032 mm, for example a vibrating screen. In one example, the screen comprises a mesh screen, a perforated screen and/or a wire screen. In one example, the drying means comprises a centrifuge.

Recirculating means

In one example, the apparatus comprises a recirculating means, arranged to recirculed water from the first aqueous suspension, wherein recirculating the water comprises capturing Cl therefrom and/or at least part of the second fraction.

In this way, the water may be reused, thereby reducing a volume of water required for the first aqueous suspension. By capturing the Cl from the water that is to be recirculated, an efficiency of removal of Cl from the particles is maintained.

In one example, the recirculating means comprises a clarifier, for example, a hydrocyclone as described above. In one example, the recirculating means comprises a centrifuge, to further separate solids from water.

In one example, the recirculating means comprises a desalination unit, for example a reverse osmosis or an ion exchanger.

Method of providing particles

The second aspect provides a method of providing particles for making a sinter for use in ironmaking and/or steel-making, the method comprising:

treating the collected particles; and recovering the treated particles;

wherein the particles before treating have a first composition comprising:

wherein the second amount of Cl is less than the first amount of Cl.

In this way, at least some Cl is removed from the particles by washing in water (i.e. the first aqueous suspension) such that the recovered, treated particles have a relatively lower amount of Cl. In this way, sinter made from the treated particles includes a reduced amount of Cl compared with the untreated particles. In turn, an amount of Cl included in the iron-making and/or steel-making is reduced. Hence, deleterious effects due, at least in part, to Cl on the iron-making and/or steel-making are attenuated. Furthermore, the inventors have determined that an amount of Cl included in particles discharged by the iron-making and/or steel-making, made using sinter including the treated particles, is also reduced, as described below in more detail. By reducing the amount of Cl included in the particles discharged by the sinter-making, iron-making and/or steel-making, an efficiency of collection thereof by electrostatic precipitation (ESP) is improved. In this way, emissions of particulates from the sinter-making, iron-making and/or steel-making to the atmosphere are lowered, since the efficiency of collection of the particles discharged therefrom is improved.

More generally, the second aspect provides a method of providing particles for making a sinter for use in iron-making and/or steel-making, the method comprising:

treating the collected particles; and recovering the treated particles;

wherein the collected particles comprise and/or are flue dust particles;

wherein the particles before treating have a first composition comprising:

wherein the second amount of Cl is less than the first amount of Cl.

In one example, a ratio of the second amount of Cl to the first amount of Cl is in a range from 1 : 2 to 1 : 10,000, preferably in a range from 1 : 5 to 1 : 5,000, more preferably in a range from 1 : 10 to 1 :1000, most preferably in a range from 1 : 20 to 1 : 500.

In this way, the second amount of Cl is significantly reduced compared with the first amount of Cl, thereby significantly reducing Cl content of the sinter.

In one example, the particles before treating have a first composition comprising:

Fe in a range from 10 wt.% to 60 wt.%, preferably in a range from 15 wt.% to 50 wt.%, more preferably in a range from 20 wt.% to 40 wt.% by weight of the particles; and/or

C in a range from 5 wt.% to 70 wt.%, preferably in a range from 25 wt.% to 60 wt.%, more preferably in a range from 30 wt.% to 50 wt.% by weight of the particles.

In one example, the particles after treating have a second composition comprising:

It should be understood that the first composition is defined as percentages by weight (or by mass) of the particles before treating and the second composition is defined as percentages by weight (or by mass) of the particles after treating. Generally, compositions described herein define total amounts of a particular element, which may be present in an elemental form and/or in a compound thereof, for example an oxide thereof. For example, for Fe, an amount of Fe is a total amount of Fe present as elemental Fe (i.e. metal), Fe₃O₄, Fe₂O₃ and/or FeO. Generally, where an amount of a particular oxide is instead defined, for example for CaO, this is the amount of the particular oxide present.

Particles discharged from iron-making and/or steel-making

It should be understood that particles discharged from iron-making and/or steel-making also refers to particles discharged from associated processes, for example sinter-making.

It should be understood that the particles comprise, substantially comprise (i.e. at least 50 wt.% by weight of the particles), essentially comprise (i.e. at least 90 wt.%, preferably at least 95 wt.%, more preferably at least 99 wt.% by weight of the particles) or consist of waste products (also known as reverts), such as discharged from sinter-making, iron-making and/or steel-making. These waste products include ferrous material and carbon material, which may be collected as particles during cleaning and filtering of off gases (also known as flue gases) from iron-making and/or steel-making processes. In one example, the particles are obtained, at least in part, from dry cyclones, skimmers or venturis as particulate removal systems within the Flue or Off Gas Plant or Overflow or underflow of hydrocyclones from downstream gas cleaning systems after wet scrubbing in iron-making and/or steel-making processes. In this way, the ferrous and carbon bearing waste products from iron-making and/or steel-making processes may be re-utilised and recycled within BF and/or BOS processes, for example. Additional materials such as mill scales, slag, road sweepings and/or fine grindings from other processes may be included in the particles to control, at least in part, the ferrous content of the sinter. Prime ores, for example milled ore concentrates, and/or coals, for example coal fines, may be included in the particles. In this way, materials of poor sintering quality, or that are environmentally deleterious to the traditional sinter plant route, may be included in the sinter, thereby providing also a potential alternative to sintering or conventional pelletising processes.

It should be understood that the ferrous material comprises iron-containing waste materials comprising at least 20 wt.% iron and/or iron ore. The ferrous material may comprise other metals, non-metals and/or oxides, carbonates, nitrides, nitrates, sulphide, sulphates and/or halides thereof. For example, the iron may be included as Fe (i.e. metal), FeO, Fe₃O₄ and/or Ρθ2θ3·

It should be understood that the carbon (also known as carbonaceous) material comprises carbon-containing waste materials, graphite, coals and/or cokes, particularly fines thereof.

Cl in sinter-making, iron-making and/or steel-making

Typically, Cl may be present in a BF, for example, as HCI, NH₄CI and/or metal salts, for example alkali metal chlorides such as NaCI and/or KCI and/or transition metal chlorides such as ZnCI. Cl may be introduced into the BF as chloride species and/or organic speciation absorbed in coke, for example. This Cl reacts with the BF gas to form HCI. At elevated HCL concentrations, reactivity of the coke decreases such that reduction of iron ore is impeded.

Without wishing bound by any theory, thermodynamic calculations suggest that Cl may accumulate and cycle in a shaft of the BF, particularly in the form of alkali metal chlorides. Superposition of two cycles has been postulated: a pure alkali metals cycle over a larger temperature range, and specific cycle, for example a KCI cycle, in a narrower temperature range from about 600 °C to about 1,000 °C.

Cl in the top gas results in corrosion of pipes, hot stoves and tuyeres. Cl in the hearth results in erosion thereof.

Hence, Cl is undesirable in a BF. For similar reasons, Cl is also undesirable in other BFsintermaking, iron-making and/or steel-making processes. As described below, Cl may also degrade an efficiency of electrostatic precipitator (ESP) collection of particles discharged from these processes.

Collecting the particles

The method comprises collecting the particles.

In one example, the method comprises collecting the particles from a primary source, for example from flue gas (i.e. directly from the flue gas discharged from a blast furnace, for example) and/or a secondary source, for example from road sweepings including the particles.

In one example, the method comprises collecting the particles from flue gas (i.e. from a primary source) by dust catching, using a dust catcher for example, by scrubbing using a wet scrubber for example, using a dry cyclone for example or a wet cyclone for example or a venture, by bag collection using a bag collector for example and/or electrostatic precipitation using an electrostatic precipitator, for example. Electrostatic precipitation is preferred.

In one example, the method comprises collecting the particles from road sweepings by sweeping using a road sweeper, for example.

Electrostatic precipitators

Generally, electrostatic precipitators (ESPs) are filtration devices for removing fine particles, for example dust and/or smoke, from flowing gases using induced electrostatic charges minimally impeding the flow of the gases therethrough.

The inventors have determined that ESP efficiency (i.e. dust collection efficiency, for example as a proportion of a dust content by weight of the inlet gas) may be depend, at least in part, on electrical resistivity due to and/or of the particles in the gas and a size distribution of the particles. While the electrical resistivity is important in an inter-electrode region of an ESP, where most particle charging occurs, the electrical resistivity is particularly important on a dust layer at a collection electrode of the ESP, where particle discharging occurs. Particles having relatively high resistivities are less readily charged. However, these charged particles also do not readily discharge at the collection electrode. Conversely, particles having relatively low resistivities are more readily charged and similarly are readily discharged at the collection electrode. Both high and low resistivities are detrimental to ESP efficiency. That is, ESPs operate more efficiently for ‘normal’ or intermediate resistivities, typically in a range from 1 x

10 to 2 x 10 ohm-cm. ESP efficiency may be significantly degraded below or above this range.

Resistivity of a particle depends, at least in part, on a composition (i.e. chemical composition) thereof, and gas conditions, for example temperature and/or moisture.

12

Marginal to high resistivity (typically between 2x10 and 1x10 ohm-cm) and high resistivity (typically above 1x10 ohm-cm) may result in adverse effects including:

1. Reduced electrostatic field strength to drive charged particles to the collection electrode. Particularly, as a dust layer builds up and the electrical charges accumulates on a surface of the dust layer, a voltage difference between the discharge and collection electrodes is reduced, thereby reducing the electrostatic field strength.

2. Back corona, in which a potential drop across the dust layer is so large that corona discharges occurs in gas trapped within the dust layer, thereby reducing ESP efficiency by as much as 50%. Resulting damage may require offline repair

3. Increased electrical sparking. When an electrical sparking rate exceeds a predetermined threshold, an ESP operating voltage is typically automatically reduced, thereby reducing ESP efficiency.

High resistivity may be reduced by adjusting gas temperature, increasing moisture content, adding conditioning agents to the gas, increasing a surface area of the collector electrode and/or using hot-side precipitators. Conditioning agents to reduce resistivity include sulfuric acid, ammonia, sodium chloride, and soda ash (also known as raw trona).

Low resistivity (typically between 10⁴ and 10⁷ ohm-cm) may reduce ESP efficiency since the charged particles are more readily discharged at the collector electrode and are recarried by the gas, rather than collected. Examples of low-resistivity dusts are unburned carbon in fly ash and carbon black (i.e. conductive particles).

Low resistivity may be increased by increasing moisture content and/or adding conditioning agents to the gas. Conditioning agents to increase resistivity include ammonia and SO₃. Resistivity may be a sensitive function of moisture content. Further, a temperature should be maintained above a dew point, to avoid corrosion of infrastructure.

Electrostatic precipitators and iron-making and steel-making

Throughout the production of molten iron or steel, large volumes of gases are formed. These gases are produced through various chemical reactions occurring within the BF, EAF or BOS for example, and are a means of removing some of the impurities from the molten iron or steel, producing a better quality product. However, as the gas travels through the BF for example, the gas entrains or captures small particles. These particles typically result from coal, coke, sinter, agglomerates and/or iron pellets that break up during transportation and loading. Typically, some of these small particles may be collected using a dust catcher and/or a gaswashing unit, for example. These collected particles, discharged from the iron-making and/or steel-making, are known as flue dust and include large amounts of ferrous material and carbon material, which may be recycled in the sinter and/or agglomerates. However, included also in the particles are undesirable elements, for example Cl, that may have detrimental effects on the collection of the particles, for example by ESP. Without wishing to be bound by any theory, it is understood that these undesirable elements, and/or compounds including such, bind to the collector electrode within the ESP, forming an insulating layer. The insulating layer reduces the electric field and hence ESP efficiency, such that emission of particulates to the atmosphere is increased. Without wishing to be bound by any theory, it is understood that the relatively large amounts of Cl, introduced into the iron-making and/or steel-making from recycled but untreated flue dust, is responsible, at least in part, for the formation of the insulating layer.

Particle size

In one example, the particles have a mean size D50 in a range from 0.001 mm to 5 mm, preferably in a range from 0.032 mm to 3.35 mm, more preferably in a range from 0.063 mm to 2 mm, most preferably in a range from 0.125 mm to 1 mm;

optionally wherein the particles have a D10 of at least 0.001 mm, preferably at least 0.032 mm, more preferably at least 0.063 mm.

In this way, the particles are suitable for sinter-making, for example.

Treating the particles

The method comprises treating the collected particles wherein treating the particles comprises removing at least some Cl therefrom by washing in the first aqueous suspension thereof, comprising the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension.

In other words, the collected particles are washed in water. It should be understood that the washing is low-pressure washing of the particles, for example substantially at atmospheric pressure, rather than high-pressure washing of the particles, for example using a pressurized water sprayer to spray water at high-pressure (for example, at least 50 bar, at least 75 bar, at least 100 bar or at least 125 bar) thereupon. Surprisingly, the inventors have determined that such low-pressure washing is effective in removing Cl, present as soluble salts, from the particles. Furthermore, such low-pressure washing may also be effective in removing other undesirable elements, present as soluble salts, for example.. Furthermore, such low-pressure washing reduces cost and/or complexity of a suitable apparatus while also being suitable for relatively high rates of treating, such as required for treating particles discharged from ironmaking or steel making.

In one example, washing in the first aqueous suspension comprises adding the collected particles to water and/or vice versa, for example in a tank, thereby forming the first aqueous suspension thereof. In one example, washing in the first aqueous suspension comprises adding water to the particles at a pressure in a range from 0.01 bar to 20 bar, preferably in a range from 0.1 bar to 10 bar, more preferably in a range from 1 bar to 10 bar, for example 5 bar, most preferably in a range from 1.5 to 3 bar. In one example, the washing is performed by flowing the first aqueous suspension in a tank.

Quantity of particles

In one example, the method comprises providing the particles in a quantity of from 1,000 tonnes to 10,000,000 tonnes per annum, preferably in a quantity from 10,000 tonnes to 1,000,000 tonnes per annum, more preferably in a quantity from 50,000 tonnes to 500,000 tonnes per annum, for example about 67,000 tonnes per annum, about 89,000 tonnes per annum or about 100,000 tonnes per annum. In this way, waste products from iron-making and/or steel-making processes may be effectively recycled, reducing and/or avoiding disposal to landfill, for example.

Rate of treating

In one example, treating the collected particles comprises treating the collected particles at a rate in a range from 250 kg per hour to 500 tonnes per hour, preferably in a range from 1 tonne per hour to 250 tonnes per hour, more preferably in a range from 5 tonnes per hour to 100 tonnes per hour, most preferably in a range from 25 tonnes per hour to 75 tonnes per hour, for example 35 tonnes per hour or 50 tonnes per hour.

In this way, a rate of treating the collected particles corresponds with a rate of collection thereof and hence according to a rate of discharge from iron-making and/or steel-making.

Pre-soaking

In one example, treating the particles comprises pre-soaking the particles before washing, for example by rinsing or showering the particles (i.e. low-pressure spraying) with water.

First fraction

In one example, treating the particles comprises rejecting a first fraction of the particles having a size of at least 5 mm, preferably at least 3.35 mm, more preferably at least 2 mm.

In one example, rejecting the first fraction of the particles is performed before washing the particles. In one example, rejecting the first fraction comprises screening (also known as sieving) the particles, for example using a screen having correspondingly-sized perforations therethrough (i.e. 5 mm, 3.35 mm or 2 mm), for example a vibrating screen.

Second fraction

In one example, treating the particles comprises rejecting a second fraction of the particles having a size of at most 0.125 mm, preferably at most 0.063 mm, more preferably at most 0.032 mm.

In one example, rejecting the second fraction of the particles is performed during and/or after washing the particles. In one example, rejecting the second fraction comprises hydrocyclonically separating the second fraction of the particles in the first aqueous suspension, using a hydrocyclone, for example, wherein the second fraction of the particles is included in an overflow thereof and the remainder of the particles is included in an underflow thereof.

In one example, the method comprises recovering the second fraction of the particles. In this way, the second fraction of the particles may be extracted from the water, enabling recirculation thereof.

In one example, recovering the second fraction of the particles comprises flocculating the second fraction of the particles, using a flocculating agent.

Recirculating water

In one example, the method comprises recirculating water from the first aqueous suspension, wherein recirculating the water comprises capturing Cl therefrom.

In one example, the method comprises adding additional water to the recirculating water. In one example, the method comprises monitoring a composition (for example, Cl content) and/or a property (for example, pH) of the water. In one example, the method comprises controlling a composition (for example, Cl content) and/or a property (for example, pH) of the water, based on a monitored (for example, Cl content) and/or a property (for example, pH) of the water, by adding an agent for controlling the composition and/or the property.

Repeated washing

In one example, treating the particles comprises repeating the washing in a second aqueous suspension thereof comprising the washed particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the second aqueous suspension.

In this way, an increased amount of Cl may be removed from the particles.

Preferred compositions

In one example, the particles before treating have the first composition comprising and/or consisting of:

Cl in a first amount in a range from 0.06 wt.% to 0.5 wt.%, preferably in a range from 0.07 wt.% to 0.4 wt.%, more preferably in a range from 0.08 wt.% to 0.3 wt.% by weight of the particles; optionally, Fe in a range from 10 wt.% to 60 wt.%, preferably in a range from 15 wt.% to 50 wt.%, more preferably in a range from 20 wt.% to 40 wt.% by weight of the particles;

optionally, C in a range from 5 wt.% to 70 wt.%, preferably in a range from 25 wt.% to 60 wt.%, more preferably in a range from 30 wt.% to 50 wt.% by weight of the particles;

optionally, Zn and/or Pb in a range from 0.001 wt.% to 5.0 wt.%, preferably in a range from 0.002 wt.% to 4.0 wt.%, more preferably in a range from 0.003 wt.% to 3.0 wt.%, most preferably in a range from 0.004 wt.% to 2.0 wt.% by weight of the particles;

optionally, Na in a range from 0.01 wt.% to 3.0 wt.%, preferably in a range from 0.02 wt.% to 3.0 wt.%, more preferably in a range from 0.05 wt.% to 1.0 wt.%, most preferably in a range from 0.10 wt.% to 0.50 wt.% by weight of the particles;

optionally, K in a range from 0.05 wt.% to 3.0 wt.%, preferably in a range from 0.10 wt.% to 3.0 wt.%, more preferably in a range from 0.15 wt.% to 1.0 wt.%, most preferably in a range from 0.20 wt.% to 0.75 wt.% by weight of the particles;

optionally, Cd in a range from 250 ppm to 5 ppm, preferably in a range from 200 ppm to 10 ppm, more preferably in a range from 150 ppm to 15 ppm, most preferably in a range from 100 ppm to 20 ppm by weight of the particles;

optionally, Ca in a range from 0.01 wt.% to 10.0 wt.%, preferably in a range from 0.02 wt.% to 9.0 wt.%, more preferably in a range from 0.05 wt.% to 8.0 wt.%, most preferably in a range from 0.10 wt.% to 7.0 wt.% by weight of the particles;

optionally, Si in a range from 0.01 wt.% to 10.0 wt.%, preferably in a range from 0.02 wt.% to 9.0 wt.%, more preferably in a range from 0.05 wt.% to 8.0 wt.%, most preferably in a range from 0.10 wt.% to 7.0 wt.% by weight of the particles;

optionally, Mn in a range from 0.01 wt.% to 5.0 wt.%, preferably in a range from 0.02 wt.% to 4.0 wt.%, more preferably in a range from 0.05 wt.% to 3.0 wt.%, most preferably in a range from 0.10 wt.% to 2.0 wt.% by weight of the particles;

optionally, Al in a range from 0.01 wt.% to 10.0 wt.%, preferably in a range from 0.02 wt.% to 5.0 wt.%, more preferably in a range from 0.05 wt.% to 4.0 wt.%, most preferably in a range from 0.10 wt.% to 3.0 wt.% by weight of the particles;

optionally, Mg in a range from 0.01 wt.% to 5.0 wt.%, preferably in a range from 0.02 wt.% to 4.0 wt.%, more preferably in a range from 0.05 wt.% to 3.0 wt.%, most preferably in a range from 0.10 wt.% to 2.0 wt.% by weight of the particles;

optionally, P and/or S in a range from 0.01 wt.% to 3.0 wt.%, preferably in a range from 0.02 wt.% to 3.0 wt.%, more preferably in a range from 0.03 wt.% to 1.0 wt.%, most preferably in a range from 0.05 wt.% to 0.50 wt.% by weight of the particles;

optionally, Ti in a range from 0.05 wt.% to 3.0 wt.%, preferably in a range from 0.06 wt.% to 3.0 wt.%, more preferably in a range from 0.07 wt.% to 1.0 wt.%, most preferably in a range from 0.08 wt.% to 0.50 wt.% by weight of the particles;

optionally, Ni, Cu, Cr, Ba, Zr, Sr, Mo, Hf and/or Co in a range from 0.001 wt.% to 1.0 wt.%, preferably in a range from 0.005 wt.% to 0.5 wt.%, more preferably in a range from 0.01 wt.% to 0.1 wt.%, most preferably in a range from 0.02 wt.% to 0.05 wt.% by weight of the particles; and optionally, Li, As, Sb, Hg and/or Br in a range from 250 ppm to 0.1 ppm, preferably in a range from 100 ppm to 0.2 ppm, more preferably in a range from 50 ppm to 0.5 ppm, most preferably in a range from 30 ppm to 1 ppm by weight of the particles; and balance oxygen, water and unavoidable impurities.

In one example, the particles after treating have the second composition comprising and/or consisting of:

optionally, Fe in a range from 10 wt.% to 60 wt.%, preferably in a range from 15 wt.% to 50 wt.%, more preferably in a range from 20 wt.% to 40 wt.% by weight of the particles;

wherein the second amount of Cl is less than the first amount of Cl.

Method of making sinter

providing a feed-sinter by binding iron ore fines, coke fines, flux fines and particles discharged from sinter-making, iron-making and/or steel-making, using a binder; and heating the feed-sinter to make the sinter and thereby discharging particles, including a ferrous material and/or a carbon material;

Sinter-making is known and hence a description is not included, for brevity.

Sinter-making provides for recycling of waste products, such as the particles discharged from iron-making and/or steel-making, as described previously. Further, sinter in a BF, for example, reduces raw flux requirements, thereby reducing coke demands, and improves furnace productivity. Hence, it is desirable to increase an amount of sinter included in a charge for a BF and hence increase production of sinter.

However, sinter-making also discharges particles (i.e. reverts), for example in off gas. As described above, Cl may degrade an efficiency of electrostatic precipitator (ESP) collection of these discharged particles. Hence, by removing Cl from the particles used in the sinter-making, the efficiency of the ESP collection is better maintained, thereby reducing particle emissions as pollution into the atmosphere.

In one example, the method comprises:

collecting, optionally electrostatically, the discharged particles; and/or wherein making the sinter comprises using, at least in part, the particles discharged from heating a previous feed-sinter.

In one example, collecting electrostatically the discharged particles comprises emitting a proportion of the discharged particles to the atmosphere, wherein the proportion of the emitted particles is reduced by at least 10 wt.%, preferably by at least 20 wt.%, more preferably by at least 25 wt.%, relative to a weight of particles emitted to the atmosphere during sinter-making using untreated particles.

In one example, collecting electrostatically the discharged particles comprises emitting a proportion of the discharged particles to the atmosphere, wherein the proportion of the emitted

3 particles is at most 40 mg/Nm , preferably at most 35 mg/Nm , more preferably at most 30

3 3 mg/Nm , even more preferably at most 25 mg/Nm , most preferably at most 20 mg/Nm .

In one example, providing the feed-sinter comprises including the particles discharged from sinter-making, iron-making and/or steel-making therein in a range from 0.1 wt.% to 20.0 wt.%, preferably in a range from 0.5 wt.% to 15.0 wt.%, more preferably in a range from 1.0 wt.% to 10.0 wt.%, most preferably in a range from 1.2 wt.% to 5.0 wt.% by weight of the feed-sinter.

Flux

The feed-sinter comprises flux fines i.e. a flux material, for example a MgO-containing flux and/or a CaO-containing flux. The flux material may be used to control, at least in part, sintering and/or the iron-making and/or steel-making.

In one example, the method comprises adding CaMg(CO₃)₂ (i.e. dolomite) and/or (Mg,Fe)₂SiO₄(i.e. olivine) to the feed-sinter as a flux, thereby providing a MgO-containing flux and/or a CaOcontaining flux.

Method of iron-making and/or steel-making

The fourth aspect provides a method of iron-making and/or steel-making, comprising: preparing a charge comprising coke, iron ore, limestone, sinter and optionally, an agglomerate for example a pellet or a briquette; and heating the charge to make iron or steel and thereby discharging particles, optionally including a ferrous material and/or a carbon material;

wherein the method comprises making the sinter according to the third aspect.

In one example, the method comprises: collecting the discharged particles;

wherein making the sinter comprises using, at least in part, the collected particles discharged from heating a previous charge.

In this way, the discharged particles may be recycled, thereby recovering Fe therefrom, while Cl may be reduced or removed therefrom.

In one example, preparing the charge comprises including the agglomerate therein in a range from 0.5 wt.% to 6.0 wt.%, preferably in a range from 1.0 wt.% to 5.0 wt.%, more preferably in a range from 1.5 wt.% to 4.0 wt.%, most preferably in a range from 2.0 wt.% to 3.0 wt.% by weight of the charge.

In one example, preparing the charge comprises including the sinter therein in a range from 10 wt.% to 95 wt.%, preferably in a range from 20 wt.% to 90 wt.%, more preferably in a range from 40 wt.% to 85 wt.%, most preferably in a range from 50 wt.% to 80 wt.% by weight of the charge.

In this way, a relatively large proportion of Fe may be recovered, for example from the collected particles discharged from the iron-making and/or steel-making.

Particles

The fifth aspect provides particles for use in making a sinter for iron-making and/or steelmaking, wherein the particles have a mean size D50 in a range from 0.001 mm to 5 mm, preferably in a range from 0.032 mm to 3.35 mm, more preferably in a range from 0.063 mm to 2 mm, most preferably in a range from 0.125 mm to 1 mm;

wherein the particles have a composition comprising:

The particles maybe be as described with respect to the first, second, third and/or fourth aspect.

Definitions

Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of’ or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like.

The term “consisting of” or “consists of’ means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of’, and also may also be taken to include the meaning “consists of’ or “consisting of’.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

Brief description of the drawings

For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

Figure 1 schematically depicts an apparatus configured for a method of providing particles for making a sinter for use in iron-making and/or steel-making according to an exemplary embodiment;

Figure 2 schematically depicts the apparatus of Figure 1, in more detail;

Figure 3 schematically depicts a graph of volumetric flow rate as a function of pressure drop for hydrocyclones having diameters in a range from 4” to 30”;

Figure 4 schematically depicts a graph of particle d50 as a function of hydrocyclone diameter;

Figure 5 schematically depicts typical particle size distributions of particles for making a sinter according to an exemplary embodiment;

Figure 6 schematically depicts graphs of Cl content of particles, before and after treating according to a method of providing particles for making a sinter for use in iron-making and/or steel-making according to an exemplary embodiment;

Figure 7 schematically depicts graphs of amounts of dust discharged from steel-making for sinter made according to an exemplary embodiment compared with convention sinter;

Figure 8 schematically depicts a method of providing particles for making a sinter for use in iron-making and/or steel-making according to an exemplary embodiment;

Figure 9 schematically depicts a method of making a sinter for use in iron-making and/or steelmaking according to an exemplary embodiment; and

Figure 10 schematically depicts a method of iron-making and/or steel-making according to an exemplary embodiment.

Detailed Description of the Drawings

Figure 1 schematically depicts an apparatus 10 configured for a method of providing particles for making a sinter for use in iron-making and/or steel-making according to an exemplary embodiment.

In more detail, the apparatus 10 is for providing particles P for making a sinter for use in ironmaking and/or steel-making. The apparatus 10 comprises a treating means 200 for treating the particles P, including a ferrous material and/or a carbon material, discharged from iron-making and/or steel-making. The apparatus 10 comprises a recovering means 300 for recovering the treated particles P. Treating the particles P comprises removing at least some Cl therefrom by washing in a first aqueous suspension thereof, comprising the particles P in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension. For convenience, input particles P (i.e. the untreated particles and/or particles to be repeatedly washed, for example) are referenced as P_in and output particles (i.e. the treated particles) are referenced as P_out in the Figures.

In other words, the particles P are washed in water W. It should be understood that the washing is low-pressure washing of the particles P, for example substantially at atmospheric pressure, rather than high-pressure washing of the particles P, for example using a pressurized water sprayer to spray water at high-pressure (for example, at least 50 bar, at least 75 bar, at least 100 bar or at least 125 bar) thereupon.

In this example, the treating means 200 comprises a tank 270 (also known as a trough, a boling box or a bath) for washing the particles P therein. In this example, the washing is performed by flowing the first aqueous suspension in and/or through a tank.

In this example, the recovering means 300 comprises a hydrocyclone 310 arranged to separate the treated particles P from water W of the first aqueous suspension, for example received from the treating means 200 via a discharge means including a pump 260.

In this example, the recovering means 300 comprises a hydrocyclone arranged to reject a second fraction F2, wherein the second fraction F2 of the particles P is included in an overflow thereof and the remainder of the particles P is included in an underflow thereof.

In this example, the recovering means 300, for example a hydrocyclone, is arranged to reject at most 10 wt.%, preferably at most 7 wt.%, more preferably at most 5 wt.%, most preferably at most 4 wt.% by weight of the particles P as a second fraction F2.

Figure 2 schematically depicts the apparatus 10 of Figure 1, in more detail.

In this example, the apparatus 10 comprises a feed means 100, the treating means 200, the recovery means 300 and a recirculating means 400.

The feed means 100 is arranged to feed collected particles P to the treating means 200. The feed means 100 comprises a feed hopper 110, a variable speed belt conveyor 120 and a main conveyor 130. The feed hopper 110 is arranged to feed particles P onto the variable speed belt conveyor 120. By varying a speed of the belt conveyor 120, the particles P may be input at a predetermined rate onto the inclined main conveyor 130. In this example, the predetermined rate is about 35 tonnes/hour. The inclined main conveyor 130 is arranged to convey the particles P to the treating means 200.

The treating means 200 is arranged to treat the particles P by washing in a first aqueous suspension thereof. The treating means 200 comprises a primary washing screen 210 including a boiling box 220, arranged to receive the particles P conveyed thereto via the inclined main conveyor 130. The primary washing screen 210 is arranged to pre-soak the particles P and transport the pre-soaked particles onto a sizing and rinsing screen 230. The sizing and rinsing screen 230 is arranged to rinse and reject a first fraction of the particles P having a size greater than 2 mm. The treating means 200 comprises a conveyor 240, arranged to convey the rejected first fraction F1 of the particles P to ground. The treating means 200 is arranged to rinse the remaining particles P (i.e. having a size of at most 2 mm) through a 2 mm screen 250 and wash the remaining particles P in a first aqueous suspension thereof in the tank 270. The treating means 200 comprises the first pump 260 arranged to pump the first aqueous suspension to the recovery means 300.

The recovery means 300 is arranged to recover the treated particles P. The recovery means 300 comprises the first hydrocyclone 310, arranged to receive the first aqueous suspension pumped from the treating means 200. The first hydrocyclone 310 is arranged to reject a second fraction of the particles P having a size of at most 63 pm, in an overflow thereof, to the recirculating means 400. The first hydrocyclone 310 is arranged to discharge by gravity the remaining particles P (i.e. having a size in a range 63 pm to 2 mm), in an underflow thereof, onto a vibrating dewatering screen 320. The vibrating dewatering screen 320 (i.e. a drying means) is arranged to remove water from the underflow, thereby recovering the treated particles P thereon. The recovery means 300 comprises a conveyor 330, arranged to convey the treated particles P to ground, for subsequent transportation to a sinter plant, for example. In this example, the treated particles P are conveyed to ground at a rate of about 30 tonnes/hour. The recovery means 300 comprises a second pump 340 arranged to pump the removed water, filtered through the vibrating dewatering screen 320, to a second hydrocyclone 350. The second hydrocyclone 350 is arranged to reject, from the removed water, a residual second fraction of the particles P having a size of at most 63 pm, in an overflow thereof, to the recirculating means 400. The second hydrocyclone 350 is arranged to discharge by gravity the remaining water in an underflow thereof, onto the vibrating dewatering screen 320.

The recirculating means 400 is arranged to filter the second fraction of the particles P having a size of at most 63 pm (i.e. super fines) and/or silts from the water and/or remove Cl therefrom and recirculate the filtered (i.e. clarified) water. The recirculating means 400 comprises a prereaction vessel 410 arranged to receive the water. The recirculating means comprises an injector, arranged to inject a measured amount of polyelectrolyte flocculant into the water in the pre-reaction vessel 410 to bind at least some of the second fraction of the particles P having a size of at most 63 pm (i.e. super fines) and/or silts and/or remove at least some of the Cl therefrom. An overflow from the pre-reaction vessel 410 comprises clarified water (about 90% of the water) and is discharged by gravity into a water tank 420, for recirculation. Lightweight contamination (for example buoyant debris) is filtered and rejected to ground by a static debris screen 430. Top up water is provided to the water tank 420 at about 4 m per hour, together with buffer and/or conditioner. The recirculating means 400 comprises a centrifuge 440, arranged to receive the water from the water tank 420 and filter at least some of the second fraction of the particles P having a size of at most 63 pm (i.e. superfines) and/or silts from the water and/or remove at least some of the Cl therefrom. Top up water is provided ο

to the centrifuge 440 at about 8 m per hour. Clarified water from the centrifuge 440 is recirculated to the treating means 200 and/or the pre-reaction vessel 410.

Hydrocyclones

Table 1 and 2 show that approximately 13 wt.% and 8 wt.% (i.e. a second fraction) of the particles (particularly flue dust) was rejected by the removal means, particularly a 20” hydrocyclone, during two weighted trials, respectively. That is, the second fraction is lost flue dust. Such relatively high levels of rejection are undesirable, as described previously.

TRIAL 1	Moisture Content (wt.%)	Tonnes	Flue Dust Lost (tonnes)
Weight In (tonnes)	17	4.55	0.59 (13 wt.%)
Weight Out (tonnes)	24	4.25
Weight @ same moisture content (tonnes)	-	3.95

Table 1: Results of first weighted trial.

TRIAL 2	Moisture Content (wt.%)	Tonnes	Flue Dust Lost (tonnes)
Weight In (tonnes)	17	5.46
Weight Out (tonnes)	24	5.37	0.46 (8 wt.%)
Weight at same M.C (tonnes)	-	4.99

Table 2: Results of second weighted trial.

This rejection is consistent with a calculated estimate of about 10 wt.% rejection for the 20” hydrocyclone at the given flow rate, for a typical particle size distribution of the particles. As summarized below in Table 3, it was found that using the particle size distribution, 9.98 wt.% of the flue dust inputted would theoretically be lost, which falls within the actual flue dust loss.

Particle Size (pm)	Make up (wt.%)	Efficiency (%)	Rejected (wt.%)	Rejected based on make up (wt.%)
2 - 4.3	1	0.56	99.43	0.99
6.2 - 8.8	1.5	2.54	97.45	1.46
12.4 - 23.8	3	15.59	84.40	2.53
33 - 44.9	15	67.17	32.82	4.92
63 - 125	53	99.87	0.12	0.067
250 - 500	24	100	0	0
1000 - 2800	2.5	100	0	0

Table 3: Particle Size Distribution of flue dust and corresponding hydrocyclone efficiencies for a 20” hydrocyclone.

The theoretical operating efficiency γ of a hydrocyclone with regards to particle sizes are shown below in Equation 1 and 2:

d_zo — 4.5

D³ _CP

L¹²(p_s-pi)

Equation 1 / ---ο 115³ \ γ = 1001 1 — e I Equation 2 where d₅₀ is a cut size (i.e. D50), Dl is a diameter of the cylindrical section of the hydrocyclone, μ is a viscosity of the liquid (i.e. the first aqueous suspension), p_s is the solid density, p₍is the liquid density and L is a length of the hydrocyclone.

Figure 3 schematically depicts a graph of volumetric flow rate as a function of pressure drop for hydrocyclones having diameters in a range from 4” to 30”.

Figure 4 schematically depicts a graph of particle d50 as a function of hydrocyclone diameter.

In order to reduce the second fraction, a reduction in hydrocyclone diameter would change the d₅₀ particle point (where the hydrocyclone is 50% efficient at removing that diameter of particle from the feed). Through reducing the hydrocyclone diameter, the d₅₀ diameter also reduces, due to an increased centripetal force experienced within the cyclone, thus forcing smaller flue dust particles to exit through the spigot (as the underflow product). Through a study, it was found that the ideal hydrocyclone diameter is 10” (i.e. 254 mm), which has an operating d₅₀particle size of 23 pm. This would result in an expected about 4 wt.% loss in solids to the overflow product, based upon the flue dust particle size distribution. However, through reducing the diameter of the hydrocyclone, the maximum operating flowrate of the cyclone is limited by pressure drop within the system. Therefore 3 cyclones of 25.4 cm diameter would be required in order to process 800 gal/min of initial water input at the washing screen, for example. Table 4 shows a summary of the percentage lost depending on particle size.

Particle Size (pm)	Make up (wt.%)	Efficiency (%)	Rejected (wt.%)	Rejected based on make up (wt.%)
2 - 4.3	1	1.26	98.73	0.98
6.2 - 8.8	1.5	8.47	91.52	1.37
12.4 - 23.8	3	51.21	48.78	1.46
33 - 44.9	15	99.38	0.61	0.091
63 - 125	53	100	0	0
250 - 500	24	100	0	0
1000 - 2800	2.5	100	0	0

Table 4: Particle Size Distribution of Flue Dust and corresponding cyclone efficiencies for a 10” hydrocyclone. Compare with Table 3.

Results

Table 5 compares typical Cl input in conventional sinter feed, as mg of Cl per kg of sinter feed, for two samples of conventional sinter CSF1 feed and CSF2 feed. The primary source of Cl is BF reverts (i.e. BF flue dust, and hence discharged particles). Hence, by removing, at least in part, the Cl from the discharged particles used for making sinter, a Cl content of the sinter is correspondingly reduced.

Cl input	CSF1 (Cl mg/kg of sinter)	SD	CSF2 (Cl mg/kg of sinter)	SD
Iron ore	6.3	3.0	5.9	1.2
BF reverts	11.9	3.1	36.5	10.9
Other reverts	5.2	1.5	10.0	2.1
Fluxes	1.5	0.3	5.3	1.5
Fuels	4.1	0.4	2.4	0.6
Total	30.4	4.8	60.0	9.4

Table 5: Cl content of sinter due to inputs.

Table 6 tabulates typical compositions of blast furnace flue dust FD1, averaged from about 16,000 tonnes. Cl content is not routinely determined but is described below with reference to Table 3.

Component	FD1
H₂0	13.29
Fe	30.51
CaO	4.42
si02	5.88
MnO	0.34
AI₂O₃	2.28
MgO	1.26
p₂o₅	0.10
K₂O	0.54
TiO₂	0.16
Na₂O	0.10
Ni	0.006
Cu	0.005
Pb	0.018
Zn	0.092
Cr₂O₃	0.12
C	40.93
s	0.286
P	0.046
LOI @ 1000 °C	41.34

Table 6: Typical compositions of blast furnace flue dust FD1.

Table 7 tabulates compositions of two samples of dry BF revert (i.e. BF flue dust, and hence discharged particles) BF1 and BF2. Typically, a first amount of Cl is in a range from 0.06 wt.% 10 to 0.5 wt.% (i.e. from 600 mg/kg to 5000 mg/kg), preferably in a range from 0.07 wt.% to 0.4 wt.%, more preferably in a range from 0.08 wt.% to 0.3 wt.% by weight of the particles.

	BF1 (mg/kg)	BF2 (mg/kg)
Fluoride	65.1	65.1
Chloride	2537.8	2597.5
Nitrite	49.8	47.9
Sulphate	444.8	399.6
Bromide	35.9	33.0
Nitrate	<LOD	<LOD
Phosphate	<LOD	<LOD
Lithium	0.3	0.4
Sodium	172.8	175.8
Ammoniun	152.7	154.8
Potassium	696.8	763.2
Magnesium	0.7	0.7
Calcium	2728.7	2642.4

Table 7: Typical compositions of dry BF revert.

Table 8 and Table 9 tabulate particle size distributions of BF revert (i.e. discharged particles). Table 8 shows a particle size distribution for >1 mm particle sizes (96.54 wt.% by weight of the particles) and Table 9 shows a particle size distribution for <1 mm particle sizes (3.46 wt.% by weight of the particles).

Blast Furnace Flue Dust Sizing Cumulative Percentages	Amount (wt.%)
+25 mm	0
+16 mm	0
+12.5 mm	0
+10 mm	0
+6.3 mm	0
+5 mm	0
+3.35 mm	0
+2 mm	0.9
+1 mm	3.3
-1 mm	96.7
AMS mm	0.54

Table 8: Particle size distribution for >1 mm particle sizes.

Flue Dust Micro Sizing Cumulative Percentages	Amount (wt.%)
+ 500 pm	9.1
+ 250 pm	35.7
+ 125 pm	64.2
+ 63 pm	85.1
- 63 pm	14.9
AMS mm	0.28

Table 9: Particle size distribution for<1 mm particle sizes.

Figure 6 schematically depicts graphs of Cl content of particles, before and after treating according to a method of providing particles for making a sinter for use in iron-making and/or steel-making according to an exemplary embodiment.

Particularly, Figure 6 shows Cl contents for 77 samples of blast furnace revert (i.e. particles discharged from iron-making and/or steel-making). Approximately 260 tonnes of such revert was discharged and collected on successive working days. The 77 samples are of the revert discharged and collected over 77 corresponding consecutive or quasi consecutive working days. For each sample, a first amount of Cl was measured before treating (Feed) and a second amount of Cl was measured after treating (Treated). Statistical data for the 77 samples is tabulated in Table 10. In this example, water was recirculated in a closed system, without desalination. A mean reduction in the Cl content due to the treating is about 61 %.

	First amount of Cl (wt.%)	Second amount of Cl (wt.%)
Mean	0.16	0.06
Minimum	0.09	0.03
Maximum	0.24	0.15
SD	0.03	0.02

Table 10: Statistical data for Cl contents for 77 samples.

Table 11 compares compositions of BF revert (i.e. discharged particles) before treating (E1) and after treating (E1*), provided according to an exemplary embodiment.

	E1 (wt.%)	Ei* (wt.%)
Moisture	20.39	24.47
Loss on Ignition	-47	-44.6
Fe	26.83	27.87
CaO	3.87	4.09
SIO2	6.2	6.63
MnO	0.26	0.27
AI₂O₃	2.73	2.8
MgO	1.15	1.24
P2O5	0.096	0.082
Cr₂O₃	0.004	0.005
K₂O	0.731	0.682
TiO₂	0.17	0.17
S	0.3	0.29
C	45.1	43.7
Na₂O	0.16	0.15
Cu	<0.005	<0.005
Ni	<0.005	<0.005
Pb	0.011	0.007
Zn	0.064	0.051
Cl	0.13	0.03

Table 11: Compositions of BF revert before treating (E1) and after treating (E1*).

A reduction in the Cl content (i.e. from the first amount of 0.13 wt.% to the second amount of 0.03 wt.%) due to the treating is about 77 %.

Figure 7 schematically depicts a graph of normalised particle emission (i.e. particles discharged into the atmosphere and not collected by ESP) from a method of making sinter according to an exemplary embodiment compared with conventional methods of making sinter. Different beds of sinter were made by a sinter plant generally using particles discharged from iron-making and/or steel making, particularly blast furnace flue dust (BFFD). Each sinter bed was made over a period of between about 10 and 20 days. Particle emissions (measured in mg/m ) from the ESP for the off gas for the sinter plant were measured daily over 450 days.

Comparative example sinter making CS1, CS2 and CS5 included conventional (i.e. untreated) BFFD in respective sinter feeds. CS2 represents making one conventional sinter bed while CS1 and CS5 each represent making multiple conventional sinter beds. For a trial, example sinter making S1 and S2 included treated BFFD in respective sinter feeds, according to the invention. S1 and S2 each represent making one exemplary sinter bed. For the trial, comparative example sinter making CS3 and CS4 included no BFFD (i.e. without BFFD) in respective sinter feeds. The particle emissions are normalised with respect to the mean particle emissions for comparative example sinter making CS1, CS2 and CS5.

Table 12 summaries blends of the sinter beds for S1, S2, CS3 and CS4. Blends of the sinter beds for CS1, CS2 and CS5 are similar to those of S1 and/or S2, as varied according to normal blending for sinter-making, as understood by the skilled person.

	S1	CS3	CS4	S2
	kg/tonne of sinter	kg/tonne of sinter	kg/tonne of sinter	kg/tonne of sinter
Mo I Rana	70	85
Lkchip		121		64
loco	106	130	263	164
Cdp				134
Tata Canada	109
Carajas	296	99	219	217
Ssft	174	100
Maf	141	86	80
Ssfg		241	284	178
Sfhg				28
Liberian			44	101
Lime Sp	29	45	37	29
Sinter fines	9	27	2	12
Olivine A/s	18	16	24	11
Hydro fines		8	6
BFFD	19			14
Millscale	7	24	22	19
Met fines	41	23	29	26
Rubble fines				9
Ibt/Spill				19
Skim/bosdeb	10	12
Lime Bp	101	89	111	102
Mag Brick	3	4
Dolomite	15	35	7	33
Fuel	29	38	43	40
P/fines	6	16	20	16
Breeze S/p	26	23	16	16
Total	1209	1222	1207	1232

Table 8: Blends of the sinter beds forS1, S2, CS3 and CS4. Sinter fines, Hydro fines, BFFD, Millscale, Met Fines, Skim/bosdeb and Mag Brick are reverts. Other terms have their usual meanings.

Table 13 summarises compositions of BFFD revert used for the sinter beds for S1 and S2.

	S1 (wt.%)	S2 (wt.%)
Moisture	15.23	17.92
Loss on Ignition	45	46.3
Fe	25.54	25.92
CaO	4.22	4.76
SIO2	6.54	6.67
MnO	0.29	0.33
AI₂O₃	2.38	2.36
MgO	1.37	1.52
P2O5	0.095	0.135
Cr₂O₃	ND	ND
K₂O	0.47	0.47
TiO₂	0.17	0.18
S	0.34	0.347
C	46.29	44.64
Na₂O	0.115	0.086
Cu	0.005	0.005
Ni	0.01925	0.025
Pb	0.0725	0.061
Zn	15.23	17.92
Cl	<0.05	<0.05

Table 13: Compositions of BFFD revert used for the sinter beds for S1 and S2.

Table 14 summaries mean normalised particle emissions from the sinter plant for making the sinters.

For sinter making using untreated BFFD, the mean normalised particle emissions for CS1, CS2 and CS5 is 1.

For sinter making without using BFFD, the mean normalised particle emissions for CS3 and CS4 is 0.64. However, making sinter without using BFFD does not recycle the BFFD nor recover Fe and/or C therefrom and is hence undesirable, as described previously. However, CS3 and CS4 are useful comparatives as practical lower limits of particle emissions.

For sinter making using treated BFFD, the mean normalised particle emissions for S1 and S2 are 0.68 and 0.76 respectively, and thus about a 28% reduction in particle emissions compared with conventional sinter making. That is, by reducing the Cl content of the sinter feed, by removing Cl from the particles used to make the sinter, the efficiency of the ESP is not degraded. That is, a greater proportion of particles is collected by the ESP and hence fewer particles are discharged into the atmosphere. In this way, atmospheric pollution is reduced. Particularly, in this way, particle emissions from the sinter making may be reduced to below 40 mg/Nm for solids.

Label	Description	Mean normalised particle emission
CS1	unwashed BFFD	1.14
S1	washed BFFD	0.68
CS2	unwashed BFFD	0.73
CS3	no BFFD	0.64
CS4	no BFFD	0.64
S2	washed BFFD	0.76
CS5	unwashed BFFD	0.98

Table 14: Mean normalised particle emissions for making sinter.

Analytical methods

Moisture content

Moisture content MC is determined by drying a nominally 100 g sample at 110°C for a minimum of 4 hours, preferably overnight.

MC =-—--X 100 % where W1 is a mass of the sample before drying and IV2 is a mass of the sample after drying.

1. Using the balance place a suitable container onto the pan and record the weight of the container (TARE weight).

2. Zero the balance, and depending on the material type, weigh out approximately 100g of the test material and note the weight (i.e. IVl).

3. Transfer the dish and contents to the drying oven (110°C) and leave fora minimum period of 4 hours, or preferably overnight.

4. Remove the dish and contents from the oven, cool and re-weigh. Subtract the initial weight of the container (TARE weight) to obtain the corrected weight (i.e. IV2).

5. Express weight loss as a percentage of original weight.

Loss on ignition

Loss on ignition LOI is determined by igniting a nominally 1 g sample at 1000°C for a 1 hour, using a platinum crucible.

LOI = (W2 - IV3) (W2 - Wl)

X 100 % where W1 is a mass of the crucible, IV2 is a mass of the crucible + sample before ignition and W3 is a mass of the crucible + sample after ignition.

1. Ignite an empty crucible in a muffle furnace at 1000°C for 10 min.

2. Remove crucible from the furnace and allow to cool in a desiccator.

3. Remove the crucible from the desiccator with forceps and carefully brush the underneath prior to placing in the balance.

Weigh the crucible to four decimal places (i.e. Wl).

Add approximately 1g of sample to the crucible and reweigh (i.e. IV2).

6. Place the crucible in the furnce and ignite at 1000°C for 1 hour.

7. Remove the crucible from the furnace and allow to cool in a desiccator.

8. Remove the crucible from the desiccator with forceps and carefully brush the underneath prior to placing in the balance.

9. Weigh the crucible (i.e. 1/3).

Carbon and sulphur

Carbon and sulphur are determined by infrared absorption, for example using a Leco CS-444, according to the manufacturer’s instructions, using a sample having a mass of about 0.2 g, against calibration standards.

The Leco CS-444 Carbon Sulphur system is a microprocessor based software driven instrument for wide range measurement of carbon and sulphur content of metals, ores, ceramics and other inorganic materials. The CS-444 uses the HF-400 induction furnace and measures carbon and sulphur by infrared absorption.

Analysis begins by weighing out a sample into a ceramic crucible on the built in balance. Accelerator material is added, the crucible is placed on the loading pedestal and the analyse key is pressed. Furnace closure is performed automatically, then the combustion chamber is purged with oxygen to drive off atmospheric gasses. After purging, oxygen flow through the system is restored and the induction furnace is turned on. The inductive elements of the sample and accelerator couple with the high frequency field of the furnace. The pure oxygen environment and the heat generated by this coupling cause the sample to combust. During combustion all elements reduced, releasing the carbon, which immediately binds with the oxygen to form CO or CO₂. Also sulphur bearing elements are reduced releasing sulphur, which binds with oxygen to form SO₂. Sample gases are swept into the carrier stream. Sulphur is measured as sulphur dioxide in the first IR cell. Carbon monoxide is converted to carbon dioxide in the catalytic heater assembly while sulphur trioxide is removed from the system in a cellulose filter trap. Carbon is measured as carbon dioxide in the IR cells , while gasses flow through both the low and high range cells. The measurement will be made only on the range selected. The low carbon range features a greater resolution carbon content as a result of the longer path length in the IR cell. In contrast , when high range carbon is selected , sample gasses flow through an IR cell with a shorter path length. The high carbon range provides a better resolution of high carbon content. The difference in path length assures optimum representation of the gasses for the range selected.

Standard	Matrix	C (wt.%)	S (wt.%)
Euro 781-1	Silicon carbide	48.25
BCS517	Iron ore		0.009
BCS 303	Iron ore sinter		0.22
Euro 877-1	Furnace dust		0.18
SX32-21	Slag		1.55
FDust 2010	Flue dust	25.3	0.20
BCS 393	Limestone		0.007
Euro 879-1	Basic slag		0.102
Euro 682-1	Iron ore		0.004

Table 8: Calibration standards for carbon and sulphur determination by infrared absorption.

Oxides

Oxides are determined by X-ray fluorescence (XRF), for example using a Bruker S8 X-ray spectrometer according to the manufacturer’s instructions, using a sample having a mass of about 0.7 g, against calibration standards.

Standard	Material type
BCS319-1	Magnesia
BCS354	Portland cement
BCS370	Magnesite-chrome refractory
BCS394	Alumina refractory
BCS528	Glass sand
Dillinger3706	Ash
EURO877-1	Furnace dust
EURO879-1	Basic slag (BOS slag)
SARM3	Refractory

Table 9: Calibration standards for oxide determination by XRF.

Element or compound	Range (wt.%)
Fe	0.05-70
CaO	0.05-100
SIO2	0.05-97
MnO	0.1 - 10
AI₂O₃	0.1 - 100
MgO	0.1 - 100
P2O5	0.02-20
Cr₂O₃	0.01 -20
K₂O	0.03-9
TiO₂	0.01 - 10
Na₂O	0.08-20
Cu	0.02-1.8
Ni	0.01 -5
Pb	0.01 -40
Zn	0.01 - 10
v₂o₅	0.02-10
ZrO₂	0.02-10
BaO	0.02-11

Table 9: Determinable ranges of elements and compounds by XRF.

Chloride and bromide

Chloride is determined by photometric analysis, for example using a Thermo Gallery Automated Photometric Analyzer according to the manufacturer’s instructions, using a sample having a mass of about 4.0 g, against calibration standards.

1. Transfer 4.0000 ± 0.0001 g of sample to a 400 ml squat beaker.

2. Add approximately 150 ml of deionised water.

3. Place a stirring rod in the beaker and cover with a watch glass.

4. Bring the solution to the boil and digest at just below boiling point with occasional stirring for 1 hour. Allow to cool.

5. Filter the solution through a paper pulp pad into a 200 ml volumetric flask, in a chlorine-free atmosphere.

6. Rinse the beaker and pad with deionised water.

7. Dilute the solution to the 200 ml mark of the flask with deionised water and mix well.

8. Pour sample into vials and place on the Thermo Gallery instrument for analysis.

Additionally and/or alternatively, Cl and/or Br at least may be determined by ion chromatography (IC), for example according to ASTM D4327 - 17 (Standard Test Method for Anions in Water by Suppressed Ion Chromatography). Ion chromatography provides for both _ _ _ —O qualitative and quantitative determination of seven common anions, F , Cl , NO₂ , HPO₄ , _ _ —2

Br , NO₃ , and SO₄ , in the milligram per litre range from a single analytical operation requiring only a few millilitres of sample and taking approximately 10 to 15 minutes for completion. Additional anions, such as carboxylic acids, can also be quantified.

ICP-OES

Additionally and/or alternatively, aluminum (Al), cadmium (Cd), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), potassium (K), sodium (Na), strontium (Sr), tin (Sn), titanium (Ti), vanadium (V), zinc (Zn), and zirconium (Zr) may be determined by inductively coupled plasma optical emission spectroscopy (ICP-OES), for example according to UOP714 - 07 (Metals in Miscellaneous Samples by ICP-OES).

Particle size distribution

The particle size distribution is measured by use of light scattering measurement of the particles in an apparatus such as a Malvern Mastersizer 3000, arranged to measure particle sizes from 10 nm to 3500 micrometres, with the particles dry-dispersed or wet-dispersed in a suitable carrier liquid (along with a suitable dispersant compatible with the particle surface chemistry and the chemical nature of the liquid) in accordance with the equipment manufacturer’s instructions and assuming that the particles are of uniform density. Particularly, the particle size distribution is measured according to ASTM B822 - 02 or ASTM B822 - 17 (Standard Test Method for Particle Size Distribution of Metal Powders and Related Compounds by Light Scattering).

Additionally and/or alternatively, the particle size distribution is measured by sieving according to ASTM E276 - 13 (Standard Test Method for Particle Size or Screen Analysis at No. 4 (4.75mm) Sieve and Finer for Metal-Bearing Ores and Related Materials). Additionally and/or alternatively, the particle size distribution for relatively coarser particles is measured by sieving according ASTM E389 - 13 (Standard Test Method for Particle Size or Screen Analysis at No. 4 (4.75-mm) Sieve and Coarser for Metal-Bearing Ores and Related Materials).

Methods

Figure 8 schematically depicts a method of providing particles for making a sinter for use in iron-making and/or steel-making according to an exemplary embodiment.

At S801, the particles, including a ferrous material and/or a carbon material, discharged from iron-making and/or steel-making, are collected.

At S802, the collected particles are treated.

Before treating, the particles before treating have a first composition comprising:

Cl in a first amount in a range from 0.06 wt.% to 0.5 wt.%, preferably in a range from 0.07 wt.% to 0.4 wt.%, more preferably in a range from 0.08 wt.% to 0.3 wt.% by weight of the particles;

Treating the particles comprises removing at least some Cl therefrom by washing in a first aqueous suspension thereof, comprising the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension.

After treating, the particles have a second composition comprising:

The second amount of Cl is less than the first amount of Cl.

At S803, the treated particles are recovered.

The method may comprise any of the steps described herein.

Figure 9 schematically depicts a method of making a sinter for use in iron-making and/or steelmaking according to an exemplary embodiment.

At S901, a feed-sinter is provided by binding iron ore fines, coke fines, flux fines and particles discharged from iron-making and/or steel-making, using a binder.

The particles are provided as described with respect to Figure 8.

At S902, the feed-sinter is heated to make the sinter and thereby discharging particles, including a ferrous material and/or a carbon material.

The method may comprise any of the steps described herein.

At S1001, a charge is prepared comprising coke, iron ore, limestone, sinter and optionally, an agglomerate for example a pellet or a briquette.

The method comprises making the sinter as described with respect to Figure 9.

At S1002, the charge is heated to make iron or steel and thereby discharging particles, including a ferrous material and/or a carbon material.

The method may comprise any of the steps described herein.

Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

In summary, the invention provides a method of providing particles for making a sinter for use in iron-making and/or steel-making is described. Particles, including a ferrous material and/or a carbon material discharged from iron-making and/or steel-making, are collected. The collected particles are treated to remove at least some Cl therefrom by washing in a first aqueous suspension thereof, comprising the particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the first aqueous suspension. The particles before treating have a first composition comprising Cl in a first amount in a range from 0.06 wt.% to 0.5 wt.% by weight of the particles. The particles after treating have a second composition comprising Cl in a second amount in a range from 0.0005 wt.% to 0.06 wt.% by weight of the particles. The second amount of Cl is less than the first amount of Cl. The treated particles are recovered. Also provided is an apparatus for providing the particles and methods of making sinter and of iron-making and/or steel making.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. An apparatus for providing particles for making a sinter for use in iron-making and/or steelmaking, the apparatus comprising:

2. The apparatus according to claim 1, wherein the treating means comprises a water supply means arranged to supply water at a predetermined flow rate in a range from 2.5 m per hour

3 33 to 25,000 m per hour, preferably in a range from 10 m per hour to 2,500 m per hour, more preferably in a range from 100 m per hour to 1000 m per hour, most preferably in a range

3 3 33 from 150 m per hour to 750 m per hour, for example 180 m per hour, 350 m per hour or 500 m per hour and/or at a predetermined pressure in a range from 0.01 bar to 20 bar, preferably in a range from 0.1 bar to 10 bar, more preferably in a range from 1 bar to 10 bar, for example 5 bar, most preferably in a range from 1.5 to 3 bar.

3. The apparatus according to any previous claim, wherein the washing is performed by flowing the first aqueous suspension in and/or through a tank.

4. The apparatus according to any previous claim, wherein the treating means comprises a first fraction rejection means arranged to reject a first fraction of the particles having a size of at least 5 mm, preferably at least 3.35 mm, more preferably at least 2 mm.

5. The apparatus according to any previous claim, wherein the recovering means comprises a hydrocyclone arranged to separate the treated particles from water of the first aqueous suspension.

6. The apparatus according to any previous claim, wherein the recovering means is arranged to reject at most 10 wt.%, preferably at most 7 wt.%, more preferably at most 5 wt.%, most preferably at most 4 wt.% by weight of the particles as a second fraction having a size of at most 0.125 mm, preferably at most 0.063 mm, more preferably at most 0.032 mm.

7. A method of providing particles for making a sinter for use in iron-making and/or steelmaking, the method comprising: collecting the particles, including a ferrous material and/or a carbon material, discharged from iron-making and/or steel-making;

treating the collected particles; and recovering the treated particles;

wherein the particles before treating have a first composition comprising:

wherein the second amount of Cl is less than the first amount of Cl.

8. The method according to claim 7, wherein a ratio of the second amount of Cl to the first amount of Cl is in a range from 1 : 2 to 1 : 10,000, preferably in a range from 1 : 5 to 1 : 5,000, more preferably in a range from 1 : 10 to 1 :1000, most preferably in a range from 1 : 20 to 1 : 500.

9. The method according to any of claims 7 to 8, wherein the particles have a mean size D50 in a range from 0.001 mm to 5 mm, preferably in a range from 0.032 mm to 3.35 mm, more preferably in a range from 0.063 mm to 2 mm, most preferably in a range from 0.125 mm to 1 mm;

10. The method according to any of claims 7 to 9, wherein treating the particles comprises presoaking the particles before washing.

11. The method according to any of claims 7 to 10, wherein treating the particles comprises rejecting a first fraction of the particles having a size of at least 5 mm, preferably at least 3.35 mm, more preferably at least 2 mm.

12. The method according to any of claims 7 to 11, wherein treating the particles comprises rejecting a second fraction of the particles having a size of at most 0.125 mm, preferably at most 0.063 mm, more preferably at most 0.032 mm.

13. The method according to claim 12, comprising recovering the second fraction of the particles.

14. The method according to any of claims 7 to 13, wherein the washing is performed by flowing the first aqueous suspension in a tank.

15. The method according to any of claims 7 to 14, comprising recirculating water from the first aqueous suspension, wherein recirculating the water comprises capturing Cl therefrom.

16. The method according to any of claims 7 to 15, wherein treating the particles comprises repeating the washing in a second aqueous suspension thereof comprising the washed particles in an amount from 2.5 wt.% to 25 wt.%, preferably in a range from 5 wt.% to 20 wt.%, more preferably in a range from 7.5 wt.% to 15 wt.% by weight of the second aqueous suspension.

17. A method of making a sinter for use in iron-making and/or steel-making, the method comprising:

wherein the method comprises providing the particles according to any of claims 7 to 16.

18. The method according to claim 17, comprising:

19. The method according to any of claims 17 to 18, wherein providing the feed-sinter comprises including the particles discharged from sinter-making, iron-making and/or steelmaking therein in a range from 0.1 wt.% to 20.0 wt.%, preferably in a range from 0.5 wt.% to 15.0 wt.%, more preferably in a range from 1.0 wt.% to 10.0 wt.%, most preferably in a range from 1.2 wt.% to 5.0 wt.% by weight of the feed-sinter.

20. A method of iron-making and/or steel-making, comprising: preparing a charge comprising coke, iron ore, limestone, sinter and optionally, an agglomerate for example a pellet or a briquette; and heating the charge to make iron or steel and thereby discharging particles, including a ferrous material and/or a carbon material;

wherein the method comprises making the sinter according to any of claims 17 to 19.

21. The method according to claim 20, wherein preparing the charge comprises including the sinter therein in a range from 10 wt.% to 95 wt.%, preferably in a range from 20 wt.% to 90 wt.%, more preferably in a range from 40 wt.% to 85 wt.%, most preferably in a range from 50 wt.% to 80 wt.% by weight of the charge.

22. The method according to any of claims 18 to 19, wherein preparing the charge comprises including the agglomerate therein in a range from 0.5 wt.% to 6.0 wt.%, preferably in a range from 1.0 wt.% to 5.0 wt.%, more preferably in a range from 1.5 wt.% to 4.0 wt.%, most preferably in a range from 2.0 wt.% to 3.0 wt.% by weight of the charge.

23. Particles for use in making a sinter for iron-making and/or steel-making, wherein the particles have a mean size D50 in a range from 0.001 mm to 5 mm, preferably in a range from 0.032 mm to 3.35 mm, more preferably in a range from 0.063 mm to 2 mm, most preferably in a range from 0.125 mm to 1 mm;

wherein the particles have a composition comprising: