Biomass direct reduced iron

Abstract

compacted 'green' briquettes between 5 cm 3 and 20 cm 3 in size comprising a composition comprising at least 30% lignocellulosic biomass material by dry weight and at least 55% iron ore fines by weight, a density between 1.4 g / cm 3 and 2.0 g / cm 3 and a compacted strength of at least 500 N. Direct reduced iron briquettes suitable for producing iron and / or steel comprise at least 85% iron by weight and at least 1% fixed carbon by weight and a volume between 7.5 cm 3 and 30 cm 3 in size, wherein said briquettes have the above composition prior to reduction (i.e. as 'green' briquettes).

Description

Technical Field

[0001] This invention relates to the production of iron.

[0002] The present invention particularly, but in no way exclusive, relates to a novel composition comprising 'green' briquettes of iron ore fines having sufficient compressive strength and raw biomass, the novel composition being suitable for subsequent conversion into direct reduced iron (DRI) in a reduction furnace.

[0003] The present invention particularly, but in no way exclusive, relates to a compacted 'green' briquette comprising fine iron ore powder and raw biomass for producing DRI in a furnace, wherein the resulting DRI has at least 85% metallic iron and at least 1% fixed carbon by weight.

[0004] This invention relates, particularly but in no way exclusive, to DRI made from the 'green' billets described above. Such DRI, for example, when hot, can subsequently be melted in a furnace to produce hot metal, which can then be cast into pig iron or further refined into steel in a metallurgical furnace. Alternatively, by way of another example, the hot DRI can be compressed between a pair of rollers having aligned pockets to form hot briquetted iron (HBI), which can then be supplied to the furnace as cold charge.

[0005] The term “direct reduced iron (“DRI”) is understood herein to mean iron produced by directly reducing iron ore (in the form of billets, lumps, pellets or fine powder) to iron using reducing gases at temperatures below the bulk melting temperature of the solid.

[0006] background

[0007] Historically, steelmaking has been a carbon-intensive process, with most of the carbon used ultimately being oxidized into CO2 and released into the atmosphere. As countries worldwide seek to reduce overall atmospheric CO2, there is pressure on steel manufacturers to find ways to produce steel without causing net greenhouse gas emissions. In particular, there is pressure to avoid using coal and natural gas, which are considered non-renewable.

[0008] Most of the world's iron is produced via blast furnaces, a technology that has existed since before the Industrial Revolution. Even with technological advancements, blast furnaces currently require approximately 800 kg of metallurgical coal per ton of iron produced and emit high levels of CO2, about 1.8-2.0 t of CO2 per ton of hot metal. The use of fossil fuels, particularly the demand for coal (in the form of coke), is an essential feedstock for blast furnace operation, and it is not possible to simply use hydrogen as a complete substitute.

[0009] An alternative to blast furnaces is the direct reduction of iron ore into a solid state using carbon monoxide and hydrogen derived from natural gas or coal. While such plants (outside India) are fewer in number compared to blast furnaces, numerous processes exist for direct reduction of iron ore. In India, coal-based rotary kilns are used to produce DRI, also known as sponge iron (accounting for nearly 20% of world DRI production), while elsewhere, gas-based vertical furnace processes tend to be used (accounting for nearly 80% of world DRI production). Gas-based direct reduction units are typically part of integrated steel mini-mills located near electric arc furnace (EAF) steel mills, but some DRI is produced from attached direct reduction units (often based on Midrex). TM Equipment for the process or based on HYL TM The equipment for the process was transported to a remote steel rolling mill.

[0010] Because DRI is typically used in electric arc furnaces, there are strict requirements on the levels of impurities in DRI, such as gangue and phosphorus, which are expensive and difficult to remove in EAF and can significantly reduce productivity.

[0011] Therefore, iron ore used to manufacture DRI is typically crushed and ground into micron-sized particles to remove gangue minerals. Such fine powder is difficult to handle (both in terms of transport and operation), so it is then agglomerated using water and / or binders to produce “green” pellets of similar size. These green pellets, after drying, are then fed into a furnace where they are sintered into hardened granules (a process known as hardening), which are subsequently supplied as feedstock to direct reduction plants (or sometimes as feedstock to blast furnaces as high-quality iron ore to help dilute gangue from the lumpy or sintered iron ore used in the blast furnace). The green pellets forming the granules have a typical compressive strength of about 10 N when wet and about 50 N when dry. As granules (after hardening), they have a compressive strength of about 2000 N.

[0012] In integrated mini-mills, natural gas-based DRIs can be thermally loaded into EAFs at temperatures in the 650°C region, thus resulting in some energy savings in terms of power and the amount of fossil fuels used. However, due to the fact that natural gas is a fuel with a lower carbon intensity than coal, the total lifetime CO2 emissions still remain at about half that of blast furnaces.

[0013] While it would be possible to use 'green' hydrogen as an alternative fuel in direct reduction equipment, green hydrogen is currently still too expensive (and not easily transportable in the required quantities).

[0014] It is known that sustainable biomass can be a complementary part of the solution, serving as an alternative to fossil fuels without causing net greenhouse gas emissions. When used, burning fossil fuels or biomass releases CO2; however, when fast-growing or regenerating plants are the source of biomass, they are largely carbon-neutral energy sources because almost the same amount of CO2 is absorbed as the plant regenerates through photosynthesis.

[0015] To date, there is no large-scale commercial ironmaking process that directly uses biomass.

[0016] Previous attempts to incorporate biomass into processes originally designed for coal (such as blast furnaces and coke ovens) have been negligible at best and generally quite disappointing in terms of overall CO2 impact. This is largely because the properties of biomass are vastly different from those of coal. For successful use of biomass, it is necessary to redesign processes around its fundamental properties.

[0017] Methods already exist in the laboratory stage (see AU 2007227635 B2 under the name of Michigan Technological University), in which billets (in the shape of bonded spherical spheres) are produced by mixing iron concentrate containing magnetite (Fe3O4) with sawdust that has been passed through a 4.75 mm sieve, mixed with a small amount of flour, and slightly moistened (to achieve agglomeration). Such composites are dried at 105°C in a process (to provide strength and stiffness). They are then placed in a furnace (which has been electrically heated) at a temperature exceeding 1375°C for the reduction of the iron ore. AU2007227635B2 states that fine powdered iron ore particles should preferably be used, and although particles with a diameter up to 0.25 inches (i.e., the typical maximum size of fine iron ore powder, 6.35 mm) or larger can be used, the processing time will be unnecessarily long, and the particles will not be suitable for themselves to form bonded lumps. AU 2007227635 B2 also states that it is preferred to use finely ground small particles, wherein fine grinding means that at least 90% of the particles will pass through a 75-micron sieve.

[0018] As noted, using such 'green' lumps would be challenging from the perspective of achieving a consistent iron ore to biomass ratio when producing DRI on a commercial scale using fine iron ore powder. Such lumps also require a drying stage to ensure they have sufficient strength to withstand the coarsening and tumbling of downstream processing (i.e., storage and final transport to the furnace of choice). While iron ore concentrates typically have high concentrations of iron oxide, significant amounts of energy are required to grind them to micron-sized particles (where they can be separated from gangue contaminants such as silica found in the host ore body).

[0019] Biomass, such as wood chips, has also been shown to reduce iron ore to solid iron by mixing it with iron ore and placing it in a furnace heated to over 800°C in a controlled atmosphere to prevent re-oxidation of the reducing material. While mixing contributes to the efficiency of the reduction process, on an industrial scale, it potentially results in a significant amount of carbon that needs to be separated from the generated DRI (unless hydrogen is used as a reducing agent). This can be further complicated by the possibility that the gas stream generated as part of the reduction process picks up fine carbon particles, leading to significant gas processing / carbon recycling challenges, or a large amount of carbon being wasted before being released into the atmosphere due to the need to clean up the process exhaust gases.

[0020] There are many possible alternative methods for producing DRI. One of these methods (currently being developed by the applicant and described in the applicant's international patent PCT / AU2017 / 051163, the disclosure of which is incorporated herein by cross-reference) involves preheating the ore and biomass billets to approximately 400°C-900°C using a furnace, such as a linear or rotary hearth furnace (or rotary kiln), thereby also causing the biomass to volatilize and removing any bound water from the ore. Under such conditions, the ore pre-reduction rate is expected to reach approximately 40%-70%. This is followed by a microwave treatment stage (in a non-oxidizing atmosphere), in which the billets are heated to approximately 1000°C-1100°C and further reduced (using residual biochar), where the reduction rate is typically approximately 90%-98% and in some cases until almost complete metallization. This DRI can then be fed into an open-arc furnace, an induction furnace, or some other form of melting vessel to produce pig iron.

[0021] The above description should not be regarded as an endorsement of common knowledge in Australia or elsewhere. Invention Overview

[0023] This invention is an alternative method for producing DRI using biomass as a feed material for direct reduction processes.

[0024] Ideally, it would be advantageous to use billets as feed material for direct reduction, where the iron ore in the billets is in the millimeter size range (often referred to as iron ore fine powder), the material can be easily mixed without the need for the addition of formal binders or water to form a dough (as part of the mixing process), and without the need for a subsequent drying step (to dry the dough material) to obtain billet strength.

[0025] The inventors have discovered that 'green' billets can be produced by mixing selected forms of biomass with fine iron ore powder and, for example, by pressing them into 'green' billets to exceed a certain density. These 'green' billets can withstand harsh treatment (as billets), namely, the roughness and tumbling of mechanical treatment for transport and processing purposes.

[0026] In some cases, existing biomass bales of certain types require specific materials to act as a binder to form the bales, which will acquire sufficient strength to maintain their integrity during such processing. The inventors have found that such a binder is unnecessary (and if used, provides only a minimal improvement in compressive strength) when used with biomass of selected forms of the present invention. However, it should be noted that the present invention does not exclude the use of binders and / or fluxes.

[0027] In the context of the preceding paragraphs, the present invention is based on the surprising realization that fine iron ore powder and lignocellulosic biomass materials, such as lignocellulosic waste biomass materials, can be mixed together without the addition of other materials acting as binders and formed into compacted lumps that have mechanical strength capable of withstanding material handling in a lump-making plant as described above, as well as being transported to and processed in a direct reduction process.

[0028] Lignocellulose waste biomass materials, such as wheat straw, rice straw, and corn straw (Kim and Dale, Biomass and Bioenergy, 26(4)361-375, April 2004) and bagasse, are some of the richest waste biomass materials among agricultural residues in the world. As an example, wheat straw is mainly composed of cellulose (28%-39%), hemicellulose (23%-24%), lignin (16%-25%), along with some ash and protein (Carvalheiro et al., Applied Biochemistry and Biotechnology, 153(1-3)84-93, May 2009).

[0029] The applicant has surprisingly discovered that when such lignocellulosic waste biomass material is mixed with fine iron ore powder (without any binder or added water when used to manufacture iron ore pellets), the resulting mixture is not only suitable for forming briquettes of the required strength for handling, transportation, etc., but also remains together during the DRI reduction process to produce DRI having at least 85% iron and 1% fixed carbon by weight. This is surprising not only from the perspective of bonding, i.e., 'green' briquettes, but also from the perspective of iron reduction and recovery and the amount of fixed carbon in the obtained briquettes.

[0030] It is speculated that by compacting the bismuth into a dense state that causes the lignocellulosic biomass material to mechanically interact with the iron ore powder, such as by tightly wrapping all the iron ore powder, a reduction rate of more than 85% can be achieved (all other conditions being equal), making it unnecessary to grind the ore particles to micrometers to obtain a good reduction rate of the ore.

[0031] This invention relates to a compacted 'green' billet that can be used as feed material for the process described in the aforementioned international patent application PCT / AU2017 / 051163. The compacted 'green' billet of this invention can also be used as feed material for other ironmaking processes and, in its DRI form, can be used as feed material for downstream steelmaking processes (subject to gangue control restrictions of different processes).

[0032] The process described above for producing DRI is collectively referred to herein as a 'direct reduction process'. The hot DRI produced in such a 'direct reduction process', which is itself compressed between a pair of rolls with alignment grooves, is collectively referred to herein as hot billet iron (HBI).

[0033] This invention relates to a compacted 'green' billet suitable for direct reduction processes, with the billet measuring 5cm. 3 and 20cm 3 Between (measured in matrix size), prior to reduction in the direct reduction process, a composition comprising at least 30% by dry weight lignocellulosic biomass material, such as lignocellulosic waste biomass material, and at least 55% by weight fine iron ore powder, at 1.4 g / cm³. 3 and 2.0g / cm 3 The density between and the compaction strength of at least 500N.

[0034] The term "dry weight" is understood in this document to refer to the weight of biomass after it has been dried using standard techniques. Many standards exist for biomass, generally revolving around heating the biomass to 105°C and measuring its weight before and after drying. One such standard is ISO 18134-3:2015. Sometimes, for lignocellulosic biomass, "dry weight" is referred to as "oven-dried tonnes (odt)".

[0035] There are many industry standards for measuring compaction strength.

[0036] The term 'fine iron ore powder' is understood herein to mean iron ore with a size between 0.15 mm (150 micrometers) and 3 mm, wherein no more than 25% by weight is contained in fine powder (below 0.15 mm). Preferably, the amount of fine powder greater than 3 mm is no more than 5% by weight. Preferably, fine powder greater than 6.35 mm is absent to avoid excessive wear on the billet pressing equipment and / or on a large number of billets that do not have the required compaction strength due to dimensional interference between the press / rollers.

[0037] The term 'biomass' is understood in this document to mean living organic matter in its original form or recently living organic matter, i.e., material in an uncarburized state.

[0038] The term 'lignocellulose' is understood herein to refer to any of several closely related substances that are essentially composed of cellulose and hemicellulose within a lignin framework. Such lignocellulose biomass can be found in forestry products and byproducts (including factory residues), agricultural products and byproducts (including residues from harvested crops such as straw and chaff waste), and / or energy crops such as sorghum, switchgrass, and sugarcane (e.g., bagasse), including short-rotation dwarf forest crops containing willow and poplar.

[0039] The preference for lignocellulose biomass materials, according to embodiments of the invention, is that their total length is less than about 6 mm in the form supplied for use as billets. Note that this preference may involve segmenting longer lengths of material into much smaller lengths.

[0040] Apart from any natural drying that occurs, there is no need to dry lignocellulosic biomass materials, although the present invention does not exclude the use of dryers, etc.

[0041] The term 'bulk' is understood in this article to mean larger than 5cm. 3 The product has a general cuboid shape with rounded edges / corners (often described as a 'pillow' shape). Such billets are typically formed by pressing / compression, although extrusion is a potential alternative in the case of segmentation (segmentation into discrete billet-sized sections). Specifically, according to the invention, spherical granules produced by spherizing material via agglomeration are not billets. Generally, a billet is defined by its "matrix size," which is the nominal volume of the billet formed by filling the cavities within the die / roller when the die / roller is fully assembled. For 5cm... 3 A typical cavity in a matrix-sized billet has dimensions of 30mm long × 24mm wide × 17mm high (at its maximum length), with rounded edges / corners. For a similar shape, a 10cm... 3 The matrix dimensions are 33mm long × 30mm wide × 20mm high. For a similar shape, 20cm... 3 The matrix dimensions are 46mm long × 34mm wide × 25mm high. In the case of "compacted" billets, their actual volume will be larger than the matrix dimensions because the dies / rollers are not actually assembled together. This is due to excess material being fed to ensure complete compaction within the voids; that is, the matching dies / rollers that create the cavities used to form the billets are kept apart from each other by this excess material. Some natural springback of the compacted material is also generally expected when released from the dies / rollers.

[0042] This invention also relates to direct reduction iron slabs suitable for producing iron and / or steel in downstream ironmaking / steelmaking processes, said slabs being formed by reducing compacted 'green' slabs described above in a direct reduction process, said slabs comprising at least 85% iron by weight and at least 1% fixed carbon by weight, and having a thickness of 7.5 cm. 3 and 30cm 3 The volume between, wherein the blank has, prior to reduction, a composition comprising at least 30% by dry weight of lignocellulose biomass material, such as lignocellulose waste biomass material, and at least 55% by weight of fine iron ore powder.

[0043] The term "fixed carbon" is understood in this document to refer to the solid combustible residue left after the billet has been heated and volatiles removed. Several industry standards exist for measuring "fixed carbon." It should be noted that the actual amount of fixed carbon achieved during processing, relative to the amount obtained through laboratory testing, can depend on a range of factors such as the heating rate. ISO 18123:2015 is a relevant standard.

[0044] The composition of compacted 'green' blocks may include non-volatile carbon materials that are not lignocellulosic biomass materials.

[0045] The non-volatile carbon material may be no more than 5% by weight of the composition of compacted 'green' lumps.

[0046] Non-volatile carbon materials can be selected such that the fixed carbon in the billet after the direct reduction process is at least 3% carbon by weight.

[0047] The amount of non-volatile carbon material can be selected such that the fixed carbon in the billet after the direct reduction process is at least 4% carbon by weight.

[0048] The composition may include at least 1% by dry weight of fluxing material, such as limestone.

[0049] The compacted block can have a “raw” compaction strength of at least 650 N, typically at least 750 N and more typically at least 850 N, which is the compaction strength at the time of formation.

[0050] The compacted billet can contain a large amount of fine iron ore powder with a size between 0.15 mm and 2.0 mm.

[0051] The meaning of the term "substantial" is difficult to quantify, but will be understood by those skilled in the art. It is difficult to quantify because, for the purposes of this invention, there are multiple options for obtaining ores with different size distributions, such as goethite, for example: screening sintered ore fines to a 2mm or 3mm fraction, crushing the sintered ore fines to 3mm / 2mm, and using tailings of sufficient quality. Each option will produce a different amount of processable fine powder.

[0052] Lignocellulosic biomass materials can be selected based on their ability to bend (i.e., fold, flex, or plastically deform) around fine iron ore powder during compaction to form a block.

[0053] Typically, lignocellulose biomass material takes the form of elongated elements that plastically deform during compaction and wrap around fine iron ore powder, thereby ensuring close contact between the biomass material and the fine iron ore powder.

[0054] Surprisingly, the inventors have discovered that the use of fine powder (as opposed to the use of all micro-fine powder) facilitates such plastic deformation and results in the interlocking of materials in the compacted billet.

[0055] Lignocellulose biomass materials can form most of the surface area of ​​compacted blocks.

[0056] Lignocellulose biomass materials can form most of the volume of compacted blocks.

[0057] Typically, lignocellulose biomass material constitutes >55% of the volume of the green block.

[0058] In any given situation, the amount of lignocellulosic biomass material is a function of many factors, including biomass type, processing ratio, etc.

[0059] Lignocellulose biomass materials can include the tubular stems of grasses.

[0060] Lignocellulose biomass materials can include wood sawdust.

[0061] Non-volatile carbon materials can include coal.

[0062] Non-volatile carbon materials may include charcoal, coke, or carbonaceous soot.

[0063] Fixed carbon can be derived from lignocellulose biomass materials.

[0064] Fixed carbon can come from other carbon sources such as coal.

[0065] The present invention is also a method for manufacturing the compacted 'green' blocks described above, the method comprising mixing lignocellulosic biomass material and fine iron ore powder together, and compacting the mixture into blocks.

[0066] This method can be performed in any suitable billet forming equipment.

[0067] The present invention also provides a direct reduction process comprising reducing the compacted billet described above in a furnace to produce iron.

[0068] Brief description of the photos and accompanying images

[0069] The invention is further described by way of example with reference to the accompanying photographs and figures, in which:

[0070] Figure 1 These are photographs of an embodiment of the present invention for producing direct reduced iron (DRI) billets from iron ore and lignocellulosic biomass materials; and

[0071] Figure 2 The diagram illustrates an embodiment of a process and apparatus according to the present invention for producing 'green' billets from iron ore and lignocellulosic biomass for subsequent reduction to produce direct reduced iron (DRI).

[0072] Description of embodiments of the billet according to the present invention

[0073] Figure 1 This is a photograph of a cross-section of a billet according to one embodiment of the present invention.

[0074] Figure 1 The blank shown is composed of lignocellulose biomass and fine iron ore powder, without any binder.

[0075] The billets are produced by mixing bagasse and iron ore of a set size and desired ratio in an Eirich horizontal high-intensity mixer, and then passing them through the Maschinenfabrik workshop at the University of Freiberg in Germany. GmbH & Co. KG uses industrial-sized briquetting machines to form briquettes.

[0076] It should be noted that the present invention is not limited to billets comprising only lignocellulosic biomass materials and fine iron ore powder. The present invention extends to billets comprising other materials such as binders.

[0077] from Figure 1It is evident that the lignocellulosic biomass material (in this case, bagasse with a particle length of 1 mm to 2 mm) has been plastically deformed around the iron ore powder (<2 mm) to tightly encapsulate the ore powder and form most of the surface area of ​​the "green block".

[0078] The inventors have discovered that using tubular stems of such lignocellulosic biomass materials, such as grass, appears to trap smaller fine particles (<1 mm) within the 'structure' of the billet without exposing them to the outer surface of the billet, thus minimizing dust formation. At the same time, it allows volatiles (generated during the heating phase between 100°C and 600°C during the production of DRI billets) to move through and escape the path of the billet in the DRI reduction process without causing excessive breakage of the billet.

[0079] When the 'green' billets according to the invention are reduced to DRI by way of example using the method described in the applicant's earlier international patent application PCT / AU2017 / 051163, they not only retain a good degree of compressive strength (especially when naturally cooled), but also have at least 85% iron and at least 1.0% fixed carbon by weight.

[0080] Having a fixed amount of carbon in the reduced billet, rather than consuming all the carbon in a reduction process, may be desirable for downstream ironmaking or steelmaking processes where the billet needs to be melted as part of the relevant process.

[0081] By way of example only, a basic oxygen furnace (BOF) relies on carbon in molten iron to reconstitute FeO, formed by driving oxygen into the bath (allowing the iron to burn efficiently), to bring the temperature to the melting point of steel, which can be above 1400°C. A DRI (in the form of HBI) with more than 2% fixed carbon, relative to pure iron with a melting point of 1538°C, potentially lowers the melting point of such a feed material to about 1400°C. Bringing the fixed carbon to 4% further lowers the melting point to about 1200°C. While a BOF relies on its main charge being molten iron, it is supplemented with scrap steel, solid pig iron, or DRI (typically up to 20% of the charge). Any method that reduces the energy required to melt the supplementary material increases the efficiency of the process and effectively reduces the amount of FeO (generated by the rapid combustion / melting process), which must either be reduced back to iron by reacting with dissolved carbon or by default discharged from the process into the slag.

[0082] The production of HBI from hot DRI via direct reduction is known in the iron and steel industry, and its briquetting machines are available worldwide, such as those from Maschinenfabrik in Germany. GmbH & Co. KG.

[0083] An embodiment of the method for manufacturing a blank according to an embodiment of the present invention

[0084] As mentioned above, in a broad sense, this invention is based on the formation of 5cm 3 and 20cm 3 Compacted 'green' blocks (in matrix dimensions) having a composition of at least 30% by dry weight of lignocellulosic biomass material and at least 55% by weight of fine iron ore powder and a strength of at least 500 N prior to reduction in a direct reduction process.

[0085] Figure 2 This is a flowchart illustrating an embodiment of the process and equipment according to the present invention for producing 'green' blocks from iron ore and lignocellulosic biomass materials.

[0086] exist Figure 2 The equipment includes a pulverizer / classifier 3 for reducing the size of the lignocellulosic biomass feed material 1 to a preferred size of less than 6 mm. The lignocellulosic biomass feed material 1 can be any suitable lignocellulosic biomass.

[0087] The pulverizer / classifier 3 can take many forms, but for manufacturing the sample blanks according to the invention in this example, an industrial pin-disc mill (e.g., capacity 2 t / h) is used, in which material is discharged through a perforated plate of 4 mm or 1 mm and oversized material is returned through the mill for further processing. All material processed by the mill is dry (during transport).

[0088] Although Figure 2 Not shown, but the lignocellulosic biomass material can be pre-cut to a set size, such as 6mm, for feeding into the crusher / classifier 3.

[0089] Once the lignocellulose biomass material is sized, it is thoroughly mixed in mixer 5 with fine iron ore powder 2 and other minor additives such as flux 20 and fixed carbon 30.

[0090] Mixer 5 can take many forms, but for the billets produced in the inventors' test work, an Eirich 175-liter horizontal high-power mixer was used in a batch mode with a mixing time of 90 seconds.

[0091] A key mixing requirement of this implementation scheme is the presence of good mixing behavior, enabling uniform mixing without separation between the ore and biomass. However, mixing is not for the purpose of agglomeration; even if the iron ore powder and lignocellulosic biomass form clumps, these clumps themselves become a cohesive mixture. The feed material to the mixer is at least 55% iron ore powder and at least 30% lignocellulosic biomass material (naturally dried) by weight. In the examples mentioned in Table 1 of the embodiments, the remainder of the mixture (besides those materials) consists of limestone or quicklime (approximately 10%), which is a flux used in downstream reduction and / or smelting / melting processes, i.e., to seek an alkalinity of approximately 1.2 (CaO / SiO2). Up to 5% is primarily non-volatile carbonaceous material (fixed carbon 30); coke, for example, may also be added to the mixture.

[0092] After proper mixing, the mixed material is fed into a screw feeder 7 located atop a pair of counter-rotating billet rollers 9, each roller having grooves of suitable size and shape machined / etched into a surface (not shown). In operation, the rollers rotate synchronously such that the grooves align in the nip between the rollers. Typically, one roller may be fixed while the other is floating and has a set force applied to it, such that a relatively constant pressure is applied to the rollers and the material passing through the nip. The required pressure can be set as needed, but generally the nip between the rollers should be minimized while still allowing fine iron particles to pass between the rollers (in the non-grooved space) without excessive crushing / grinding. That is, the purpose of the rollers is not to crush or grind the iron ore particles, but to apply sufficient force so that the feed material will tend to flow into the grooved sections of the rollers.

[0093] Suitable briquetting machine suppliers are available worldwide, but for the briquettes produced for the test work in this example, those from Maschinenfabrik in Germany were used. A machine with a screw feeder from GmbH & Co. KG.

[0094] After the mixture passes through the rollers, a fully formed, compacted 'green' billet is observed. This means that billets larger than the volume of a single groove (but not twice its volume) are observed.

[0095] Typically, the billets are joined together by relatively thin skirts (shirts) of feed material between them. This is done to ensure that there is always an excess of mixture to fill the grooves and that the billets have been properly compacted.

[0096] It is not uncommon to observe some variation in the density of individual billets across the rolls due to the changes in feed between the rolls during the compression of the mixture passing between the rolls; that is, in practice, the feed to the edge of the roll may be lower.

[0097] As the billet passes down the rollers, it typically breaks and is sized to fit its set matrix dimensions. Waste from this breakage passes through a selected screen / sieve 13 and is then fed back to the screw feeder. Alternatively, this waste material can be returned to the crusher / mixer 3. The simple fall of the billet after compaction typically results in breakage as waste is generated.

[0098] It should be noted that it is important that the compressive strength of the billet is sufficient to withstand the static weight loads and resistance effects generated by downstream processing in the direct reduction unit, which will typically have a fixed bed configuration, although the use of a rotary kiln is not excluded.

[0099] For the test sample results provided in Table 1 of the embodiments, after excluding the maximum and minimum results, 12 individual billets were tested and averaged.

[0100] It should also be noted that it is important that the billet can withstand handling and transportation without excessive crushing. To simulate this performance requirement, 2 kg billets of each test sample were dropped from a height of 2 m four times, with fine powder being sieved out after the second and fourth drops.

[0101] Example - 'Green' billet according to an embodiment of the present invention

[0102] The inventor directed extensive testing work on the following:

[0103] (a) Forming "green" blocks of lignocellulose biomass and iron ore powder using different lignocellulose biomass materials and different ratios of lignocellulose biomass materials and iron ore powder; and

[0104] (b) Extensive testing work on 'green' billets.

[0105] Figure 2 The above description explains how 'green' blanks are formed and tested.

[0106] Figure 1 The photo shows such a 'raw' blank.

[0107] Table 1 provides examples of selected compositions of various lignocellulosic biomass materials' 'green' blocks that were tested.

[0108] Table 1

[0109]

[0110] Table 1 also provides the properties (density and strength) and performance (crushing test results) of the tested 'green' billets.

[0111] It is evident from Table 1 that suitable 'green' blocks can be formed from a series of lignocellulosic biomass materials with different ratios of lignocellulosic biomass material and iron ore fines, and in the case of sample T.04, coal is used as part of the mixture.

[0112] As mentioned above, the testing was conducted under the inventor's guidance. The inventor's experience allowed them to extrapolate results across the range of lignocellulose and iron ore powder ratios described in the specification.

[0113] Many modifications can be made to the implementation scheme described above without departing from the spirit and scope of the invention.

Claims

1. A compacted 'green' billet suitable for direct reduction processes to produce direct reduced iron, wherein, prior to reduction, the 'green' billet has a general cuboid shape with rounded edges / corners and a diameter of 5 cm. 3 and 20 cm 3 The volume of the composition, comprising at least 30% lignocellulosic biomass material and at least 55% iron ore powder by dry weight, is at 1.4 g / cm³. 3 and 2.0 g / cm 3 The density between and a compaction strength of at least 500 N, and wherein the lignocellulosic biomass material is wrapped around the iron ore powder.

2. The compacted 'green' block according to claim 1, wherein the lignocellulosic biomass material is folded, flexed, or plastically deformed around the iron ore powder.

3. The compacted 'green' block according to claim 1 has a compaction strength of at least 850 N.

4. The compacted 'green' block according to any one of the preceding claims, wherein the lignocellulosic biomass material forms the majority of the surface area of ​​the 'green' block.

5. The compacted 'green' block according to claim 4, wherein the lignocellulosic biomass material comprises the tubular stems of dried grass.

6. The compacted 'green' block according to claim 4, wherein the lignocellulosic biomass material comprises sawdust.

7. The compacted 'green' block according to claim 4, wherein the lignocellulosic biomass material comprises dried grass tubular stems and sawdust.

8. The compacted 'green' billet according to claim 1, wherein a large portion of the iron ore fine powder is between 0.15 mm and 2.0 mm.

9. A direct reduction iron billet suitable for producing iron and / or steel in downstream ironmaking / steelmaking processes, said direct reduction iron billet comprising at least 85% iron by weight and at least 1% fixed carbon by weight, and having a thickness of 7.5 cm. 3 and 30 cm 3 The volume between, the billet comprises, prior to reduction, a compacted 'green' billet as described in any of the preceding claims, the billet further comprising at least 1% lime material for melting the slag in the downstream ironmaking / steelmaking process.

10. The direct reduction iron billet according to claim 9, wherein the billet further comprises a non-volatile carbon material prior to reduction, the material being not a lignocellulosic biomass material.

11. The direct reduction iron billet according to claim 10, wherein the billet contains no more than 5% non-volatile carbon material before reduction.

12. The direct reduced iron billet according to claim 10, wherein the amount of the non-volatile carbon material is selected such that the fixed carbon of the direct reduced iron billet is at least 3% carbon by weight.

13. The direct reduced iron billet according to claim 12, wherein the amount of the non-volatile carbon material is selected such that the fixed carbon of the direct reduced iron billet is at least 4% carbon by weight.

14. The direct reduced iron billet according to any one of claims 10 to 13, wherein the non-volatile carbon material comprises coal.

15. The direct reduced iron billet according to any one of claims 10 to 13, wherein the non-volatile carbon material comprises char, coke, or carbonaceous soot.

16. A method for manufacturing compacted 'green' billets suitable for a direct reduction process to produce direct reduced iron according to any one of claims 1 to 8, comprising mixing the lignocellulosic biomass material and the iron ore powder together, and compacting the mixture into billets of a generally cuboid shape in a pair of counter-rotating billet rollers having grooves of suitable size and shape machined / etched into the face.

17. A direct reduction process comprising reducing 'green' billets according to any one of claims 1 to 8 in a furnace and producing iron.

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