Injection lance for pulverized coal and other granular material

Abstract

An injection lance (10) for feeding granular material into a shaft furnace comprises: a single tube (12) extending along a longitudinal axis (A), the tube being hollow and having an axial end opening (18), referred to as discharge opening, through which, in operation, a stream of granular material and conveying gas is discharged. A staging section (20) is arranged at a predetermined distance from the discharge opening and comprises at least one injection port (22) extending through a wall of the tube to generate at least one radial stream of granular material and conveying gas exiting the lance through said injection port(s) upstream of the discharge opening. The injection lance is particularly adapted for feeding pulverized coal into a tuyere of a blast furnace.

Description

[0001] INJECTION LANCE FOR PULVERIZED COAL AND OTHER GRANULAR

[0002] MATERIAL

[0003] Technical field

[0004] The present invention generally relates to an injection lance for use in shaft furnaces and blast furnaces, in particular for feeding pulverized coal into a tuyere of a blast furnace.

[0005] Technical problem

[0006] Pulverized coal injection (PCI) is a process which involves injecting large volumes of fine coal particles into the raceway of the blast furnace. Pulverized coal is an important auxiliary fuel used in the Blast furnace ironmaking. PCI provides auxiliary fuel for partial coke replacement and has proven both economically and environmentally favourable. It can result in substantial improvement in the blast furnace efficiency and thus contribute to the reductions of energy consumption and environmental emissions.

[0007] The PCI process is based on the simple concept of carrying the finely ground (pulverized) dried coal by a conveying gas (normally nitrogen) to blast furnace where it is distributed to different tuyeres and injected through a lance in the blow pipe. In the blow pipe, it is mixed with oxygen enriched hot blast air and then supplied to the blast furnace in the raceway.

[0008] Historically, the PCI lance is a simple tube, i.e. a hollow cylindrical tube. The mixture of pulverized coal with conveying gas is introduced at one axial end and discharged at the opposite end.

[0009] In the interests of ecological and economic optimization, so called oxy-coal combustion was developed to promote faster combustion with higher burnout rate. The oxy-coal lance differs from the simple lance by double tube structure: an inner tube for conveying the pulverized coal with conveying gas and an outer tube, surrounding the inner tube, for conveying (pure) oxygen. A disadvantage of this technology is increased safety risks due to the oxygen supply hose being close to the blast furnace. The oxy-coal lance designs are for example described in US 2007 / 205,543 AA. To improve the combustion efficiency, this oxy-coal lance includes means for swirling the oxidant, which consists of six evenly-spaced spiral-like passages (grooves) machined into the outer surface of the inner tube.

[0010] EP 2 038 433discloses a double tube lance that comprises holes or axial slits arranged in the inner tube upstream of the axial discharge aperture to promote early mixing of coal and combustion air, resulting in an increased combustion efficiency. EP 2 796 566 discloses a double walled lance with similar axial slits in the tip of the inner tube, and discusses in detail the mixing effect provided by such slits.

[0011] Hence, a great deal of effort has been spent on oxy-coal lances to improve the combustion efficiency of the injected coal particles.

[0012] However, the simple-tube lance design is still vastly used in the industry and there remains a need to improve the combustion efficiency in this technology.

[0013] Object of the invention

[0014] Consequently, the object of the present invention is to provide an injection lance of improved design and that particularly improves the combustion efficiency of pulverized coal without the requirement of pure oxygen to achieve this goal.

[0015] General Description of the Invention

[0016] This object is achieved by an injection lance as claimed in claim 1 .

[0017] The invention provides an injection lance for feeding granular material into a shaft furnace I blast furnace, and particularly into a tuyere (or tuyere assembly) of a blast furnace. The lance has been particularly designed for feeding pulverized coal to the blast furnace, but may be used for feeding other granular materials into the furnace that need gasification I partial or complete oxidation. The lance comprises a single tube extending along a longitudinal axis, the tube being hollow and having an axial end opening, referred to as discharge opening, through which, in operation, a stream of granular material and conveying gas is discharged.

[0018] According to the invention, the lance comprises a staging section that is arranged at a predetermined distance from the discharge opening and comprises at least one injection port extending through the wall of the tube to generate at least one radial stream of granular material and conveying gas exiting the lance upstream of the discharge opening.

[0019] The inventive lance is based on a single walled lance design and comprises a staging section through which PC is ejected from the lance before its tip (axial end). As will be discussed in more detail below, the staging section generates a secondary flow around the primary flow exiting through the discharge opening, which reaches higher temperatures and higher burnout rate (burning efficiency). This secondary flow acts synergistically on the primary flow and results in a higher average temperature of the global PC flow ejected from the lance, and hence improved burnout rate.

[0020] The term single tube means that the lance has a single tube configuration, generating an axial cylindrical (pipe) stream. The tube has a hollow cylindrical body with an inner surface that defines a flow passage for the mixture of PC and conveying gas, whereas the outer surface of the tube (with the staging section and up to the discharge opening) is exposed to the hot blast. Hence there is no double tube structure, respectively no other coaxial tube arranged inside or surrounding this single tube. In other words, the injection ports of the staging section are uncovered, in particular not covered by an outer tube surrounding the single tube.

[0021] In embodiments, the staging section comprises a plurality of injection ports that extend through the tube wall and are circumferentially distributed therein to generate a plurality of radial streams of granular material and conveying gas exiting the lance through said injection ports upstream of the discharge opening. It may also be said the injection ports form staged injection nozzles that nozzles allow granular material to exit the lance radially and mix in the staged mixing zone surrounding the lance. The staged mixing zone (region) is where the granular material / coal coming from the staged injection nozzles mixes with the hot blast, upstream of the discharge opening where the remaining part of the coal is injected in axial direction.

[0022] In general, the granular material may be fine or coarse particulate material and in bulk form. For example, fine particulate material may refer to particles with a particle size lower than 3 mm. Coarse particulate material may refer to particles with a particle size lower than 10 mm and greater than 3 mm. The term particle size may refer to the median grain size (D90). It may be measured using standard ASTM C136 or more specifically for coals ISO 1953.

[0023] The granular material may comprise or consist of particles of coal, biochar or plastic, or a mixture thereof. In particular, coal may be pulverized coal (i.e. fine particulate). The biochar may be fine-grained. The plastic material may for example be plastic RDF (Refuse-Derived Fuel), typically coarse-particulate.

[0024] In embodiments, the injection ports of the staging section are arranged in one or more planes transversal to the longitudinal axis. There each plane may comprise between 2 and 15 injection ports.

[0025] The axial extent (length) of the staging section hence depends on the amount and design of the injection ports and in particular on the number of planes. In practice the staging section may extend over a length of up to 200 mm.

[0026] The predetermined distance between the discharge opening and injection port(s) is at least 5 mm, preferably between 15 and 150 mm. Two adjacent planes of injection ports may be spaced by a distance of between 5 and 100 mm. In other words, the predetermined distance between the discharge opening and the closest injection ports is of at least 5 mm, and e.g. 15 mm to 150 mm. As the injection ports are within the staging section, the predetermined distance between the staging section and the discharge opening is the same. So, in practice, the staging section is located proximal to the discharge opening, remote form the feed opening.

[0027] Advantageously, the injection lance comprises deflection means configured to promote ejection of granular material through the at least one injection port in the staging section. The deflection means may take any form appropriate to deviate part of the stream of granular material and conveying gas toward the one or more injection ports. The deflection means can include hole-specific features, i.e. individual elements near predetermined injection holes to direct the stream toward the latter. Alternatively, the deflection means can include global deflection features, i.e. that configured to promote deviation of granular material toward a group of injection ports, preferably all of them. For example, hole-specific features may include angled plates or baffles placed near each injection port, or at least part of them, to direct granular material towards the injection ports.

[0028] In embodiments, a constriction is arranged within the tube in-between the discharge opening and the coal staging section to control the proportion of pulverized coal discharged through the injection ports. Such a constriction placed downstream of the coal staging section forms a global deflection means able to promote ejection through the plurality of injection ports.

[0029] In practice, the constriction can take the form of an annular bead defining an orifice of reduced diameter. The inner diameter of the lance is thus locally reduced. Alternatively, the constriction can be obtained by a reduced internal diameter of the tube from the discharge opening up to the coal staging section.

[0030] The deflection means may further comprise helical ribs I grooves inside or outside the tube, and / or sloped internal surfaces inside the tube, which can provide global effects to promote ejection through the coal staging section.

[0031] The constriction in the tube controls the distribution of the PC flow towards the injection ports in the staging section. Indeed, the constriction creates a counter pressure that diverts a branching flow towards the injection ports.

[0032] In embodiments, the constriction is configured to define a staging ratio between 5 wt.% and 75 wt.%, which is defined as the ratio of the granular material mass flow through the injection ports over the total granular material mass flow through the lance.

[0033] Such staging ratio can be obtained by adapting the flow cross-section offered by the injection ports. Accordingly, the ratio of the cumulated flow cross-section through the injection ports over the total flow cross section through the lance, i.e. cumulated flow cross-section though the injection ports and the constriction, may be controlled to lie between 5 and 75%.

[0034] In embodiments, the lance further comprises swirl generating features arranged inside and / or outside the tube and extend from the discharge opening to over the staging section, and preferably further beyond. This creates a swirling motion in the flow passing through and / or around the lance, resulting in an extensive spread of the flow as it exits the end of the lance.

[0035] The swirl generating features may comprise a helical groove on an interior tube surface and / or a helical groove on an external tube surface. Those grooves may have same or different helix angle. In general, the helical groove may have a helix angle between 5 and 85°, preferably 20° to 60°.

[0036] In embodiments, the tube may have an inner diameter between 10 to 100 mm.

[0037] In embodiments, the cumulative flow cross-section defined by the injection ports in the staging section may be between 5 mm2and 2000 mm2.

[0038] In embodiments, to give a swirling motion, the injection ports may be inclined relative to the longitudinal axis, for example by an angle of 10° to 170° relative to the length axis.

[0039] In case the lance comprises an outer helical groove, the injection ports may be arranged within the groove and follow its helix angle.

[0040] The above and other embodiments are recited in the appended dependent claims.

[0041] According to another aspect, the invention relates to a blast furnace comprising at least one tuyere assembly equipped with the present injection lance.

[0042] According to a further aspect, the invention relates to the use of the present injection lance for injection of granular material into a shaft furnace or blast furnace.

[0043] According to a yet another aspect, the invention relates to a tuyere assembly for a blast furnace, the tuyere assembly defining a hot blast channel therein for carrying hot blast wind, the tuyere assembly equipped with an injection lance according to any of the preceding claims, wherein the injection lance is arranged to protrude inside the hot blast channel such that the staging section (20) and discharge opening are exposed to the hot blast wind. The tuyere assembly may generally comprises a blow pipe and a tuyere. The tuyere end is arranged through the blast furnace wall and is connected at the opposite end to a blow pipe that is in commincation with an annular bustle pipe. Depending on the application, the discharge opening and staging section can be arranged in the blow pipe or tuyere. Brief Description of the Drawings

[0044] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0045] Fig. 1 is a perspective view of an embodiment of the pulverized coal injection lance according to the invention;

[0046] Fig. 2 is a longitudinal cross-sectional view of part of the lance of Fig.1 ;

[0047] Fig. 3 is a CFD simulation image illustrating the particle flow during operation of the lance;

[0048] Fig. 4 is a CFD simulation image showing PC stream ejected through the discharge opening;

[0049] Fig. 5 CFD simulation image showing the radial PC streams ejected through injection ports;

[0050] Fig.6 is a graph illustrating the evolution of the particle temperature as a function of the distance from the lance tip for the streams of Fig.4 and 5; and

[0051] Fig. 7 is a plot of the burnout rate vs. distance from the lance tip, for the inventive lance and for a prior art lance.

[0052] Description of Preferred Embodiments

[0053] An embodiment of the present injection lance will now be described in the context of the blast furnace, and specifically for injection of pulverized coal (PC).

[0054] As is well known, in the process of iron production, a blast furnace is outfitted with several injection points, known as tuyeres. These are placed around the furnace’s circumference and serve as injection points for high-temperature blast air (around 1200°C), pulverized coal, and possibly other reducing agents. Prior to the tuyere penetrating the blast furnace, the pulverized coal is introduced into the blast air by means of a lance (injection lance), where it reacts with the air. Maximizing combustion efficiency is crucial, particularly when injecting large amounts of pulverized coal, to minimize the presence of unburnt coal at the blast furnace’s top outlet. There are two key mechanisms to increase the burn-out rate of the coal particles:

[0055] - rapid heating of the coal particles, which accelerates the rate of moisture removal, devolatilization, and pyrolysis, collectively leading to a quicker combustion rate.

[0056] - effective mixing of coal with oxygen. The more extensively the coal and oxygen are mixed, the higher the likelihood of a carbon atom reacting with an oxygen atom.

[0057] The present PC injection lance enhances combustion properties compared to the conventional single tube design of injection lances, marking a significant improvement. A perspective view of an embodiment of the present pulverized coal injection lance 10, or simply lance, is illustrated in Figures 1 and 2. The lance 10 consists of a single tube 12 that extends along a longitudinal axis A. The tube 12 has a hollow cylindrical body - forming the tube wall - which may be of circular cross-section. The inner surface 14 of the tube 12 defines a flow passage 14 for a stream of pulverized coal and conveying gas, which is open at both axial ends. The tube 12 may, by design have predetermined wall thickness T12 and an inner diameter D12. The outer surface 16 of tube 12 is the outer surface of the lance 10. Hence, the outer diameter D16 of tube 12 is the overall maximum diameter of the lance 10, and we generally have (D16-D12) / 2 = T12. The inner diameter D12 may lie between 10 and 100 mm. The wall thickness T12 may e.g. lie between 1 and 12 mm, in particular 2 and 5 mm.

[0058] In use, the pulverized coal is carried through the lance 10 by means of the conveying gas. The mixture of coal and gas is fed from one axial end opening of the lance, referred to as feed opening, travels through the flow passage 14, and is discharged through the opposite end opening, referred to as discharge opening 18.

[0059] The tube 12 may be made from metal, in particular high-grade stainless steel or nickel alloy, or ceramic materials. The tube, with its features, can be advantageously manufactured by additive manufacturing.

[0060] A total length L1 (not shown) of the lance 10 from the feed opening to the discharge opening may range from 1 to 4 m. In use, the lance 10 is arranged to protrude inside a tuyere or blow pipe of the blast furnace. The protruding length L2 (see Fig.3) of the lance may be between 0.1 and 1 m.

[0061] The feed opening is not shown in Fig.1 . It may be coupled to a feed piping by any suitable way (e.g. mechanical coupling or welding), in turn connected to particulate coal supply arrangement comprising a coal mill and pneumatic system. For example, the PC may have a particle size in the range of 0.001 to 3 mm. The conveying gas may be an inert gas, e.g. nitrogen and / or CO2, possibly mixed with compressed air. The mixture of PC and conveying gas is supplied under pressure high enough to overcome the counter pressure at the injection point and the pressure losses of piping and the injection lance. Typically, the supply pressure may be between 0.5 and 40 bar.

[0062] It will be appreciated that the lance 10 comprises a staging section 20 - here referred to as coal staging section - arranged at a predetermined distance L3 from the discharge opening 18. The coal staging section 20 comprises a plurality of injection ports 22 that extend through the tube wall and are circumferentially distributed around the tube. The staging section 20 is thus proximal to the discharge opening 18, positioned upstream thereof. As can be seen, the staging section 20 starts with the first injection ports 22 at distance L3 from the discharge opening 18.

[0063] In the shown embodiment, the coal staging section 20 comprises six injection ports 22 arranged in one plane transversal to the longitudinal axis A. In other embodiments, the coal stating section may comprises two or more planes of injection ports, each having e.g. 1 to 15 injection ports 22.

[0064] The injection ports 22 are holes formed through the tube wall thickness to allow ejection of PC propelled by the conveying gas. The injection ports 22 may also be referred to as ejection ports.

[0065] Thus, the injection ports 22 operate in parallel to the discharge opening 18, generating a plurality of radial streams of pulverized coal and conveying gas that are discharged from the lance upstream of discharge opening. These streams are referred to as radial streams, since they do not exit the lance axially but with a predetermined angle relative to axis A. However, as will be mentioned below, the angle of the radial streams relative to axis A is normally less than 90°, in particular to have a forward orientation of the radial streams, toward the discharge opening.

[0066] Hence, in operation a primary flow of PC is discharged axially at the front end of lance 10 through the discharge opening 18 and a secondary flow is formed around the lance by the injection ports of the coal staging section that generate radial streams of PC. The secondary flow leads to a broader dispersion of the coal, resulting in rapid heating and consequently faster combustion.

[0067] Indeed, coal particles discharged through injection ports 22 are prematurely discharged into the tuyere, being carried by the hot blast wind (around 1200°C) toward the blast furnace. These coal particles are thereby transported on a slightly longer path in the tuyere before reaching the combustion zone of the blast furnace, compared to the coal particles ejected by the discharge opening 18. Thus, they are submitted to an earlier heat transfer by convection and radiation which results in an increase of particle temperature, which facilitates their ignition and thus enhances the combustion efficiency of the pulverized coal.

[0068] As better seen in Fig.2, the lance comprises a constriction 24 that is arranged inside the tube 12 in-between the coal staging section 20 and the discharge opening 18. Here, the constriction 24 is disposed contiguous to the coal staging section 20.

[0069] The constriction 24 is formed by an annular bead protruding from the inner surface 14 of the tube 12, leading to a local increase in tube wall thickness. The constriction 24 thus forms an orifice-type flow restriction along the flow passage 13. The localized narrower flow cross-section defined by constriction 24 is indicated D24. In the embodiment, the tube 12 thus has a nominal / design inner diameter D12 throughout its length, except at the level of the constriction where the flow diameter is D24 (<D12).

[0070] The constriction allows controlling the split between the portion of PC / gas mixture that flows to the discharge opening 18 and the part that is ejected through the coal staging section 20. The constriction, respectively diameter D24, may be sized to allow a level of coal staging between 5 wt.-% and 75 wt.-%, which is defined as the ratio of the secondary flow (i.e. total mass flow through the injection ports) over the total PC mass flow through the lance. The lance may further comprise swirl generating features arranged inside and / or outside the tube, which extend from the discharge opening to over the coal staging section, and typically further beyond. In the shown embodiment, the tube 12 comprises a helical groove 26 provided on the inner tube surface 14 whereas a helical groove 28 is provided on the outer tube surface16.

[0071] As can be seen, helical grooves 26, 28 here have the same inclination angle (helix angle) relative to axis A, which may generally lie between 5 and 85°, in particular 20° to 60° relatively to the axis A.

[0072] This preferred interval enhances the efficiency of the interaction between the grooves and the particles passing through them.

[0073] In terms of construction, it may be observed that the grooves locally reduce the thickness of the tube wall. Therefore, the inner and outer helical grooves are slightly offset circumferentially, to limit the reduction of the tube’s wall thickness.

[0074] In operation, the particles flow through the lance 10 where the helical grooves 15 act as obstacles to the flow, disrupting its regular movement. This creates an alternative of high and low pressure areas along the lance inducing a swirl, mixing the fluid more efficiently and promoting particle ejection / dispersion.

[0075] Fig.3 shows a simulation of the PC flow discharged by the lance 10, where the lance 10 is installed in a tuyere assembly 30 of a blast furnace (not shown). In the figure, the lance 10 is actually introduced through an aperture 32 in the wall of a blow pipe 6. The lance 10 points towards the blast furnace and protrudes inside the blow pipe and mainly inside the tuyere 7.

[0076] As can be observed, the PC is already ejected from the lance 10 before the lance tip, and the PC stream in front of the lance forms a conical plume that is notably wider than the diameter D16 of the lance.

[0077] This plume shape of Fig.3 results from the combined primary and secondary flows that are shown individually in Figs. 4 and 5, respectively. Whereas at the discharge opening 18 a rather dense axial stream of PC exits the lance, it can be observed that the coal staging section 20 produces a secondary flow of PC that, as understood surrounds the axial, primary stream. In the simulation illustrated in Figs. 4 and 5, the lance is designed (namely restriction 24) to operate with a coal staging ratio of 25 wt.%, i.e. 25 wt.% of the PC exits through the injection ports whereas 75 wt.% of the total PC discharged by the lance is ejected through the discharge aperture 18. Refence sign 2 indicates the secondary flow and reference sign 1 the primary flow.

[0078] As will be understood, the coal particles 2 exiting the lance 10 through the injection ports are introduced earlier into the hot blast. Compared to the particles 1 exiting at the lance tip, they will thus heat up faster and follow a longer path to the blast furnace interior, hence more time to combust.

[0079] As observable from Fig. 6, the coal particles 2 exiting the lance 10 through the injection ports are rapidly heated to high temperatures by the hot blast, here above 400°C when they reach the tip of the lance (where a temperature difference of more than 300°C exists compared to the particles of the primary flow exiting the lance through the axial discharge opening 18). The heat increase of the secondary flow 2 continues as the particles travel towards the blast furnace, and the temperature remains significantly superior to that of the primary flow 1 (which is comparable to that of a conventional single tube lance with only 1 axial flow).

[0080] The increased temperature of the secondary flow 2 facilitates its ignition and therefore improves the combustion rate of those coal particles. It also has a synergistic effect with the primary flow that is surrounded by hotter and more flammable particles. This results in an increase of average temperature for the whole plume of pulverized coal (flows 1 + 2), which in turn results in an increased burnout rate.

[0081] In Fig. 7, the burnout rate of the global PC flow ejected by the inventive lance 10 (i.e. flows 1 +2, see curve 3) is compared to the PC flow ejected from a conventional single tube lance (only end aperture generating a single axial flow - see curve 4). The graph indicates that the inventive lance 10 with the coal staging section allows for a more rapid burnout than the traditional design and thus a comparative advantage. At a distance of 0.3 m from the lance tip, the burnout rate is increased by about 10%.

Claims

Claims1 . An injection lance for feeding granular material into a shaft furnace, in particular for feeding pulverized coal into a tuyere of a blast furnace, said lance (10) comprising: a single tube (12) extending along a longitudinal axis (A), the tube being hollow and having an axial end opening (18), referred to as discharge opening, through which, in operation, a stream of granular material and conveying gas is discharged; characterized in that a staging section (20) is arranged at a predetermined distance from the discharge opening, said staging section comprising at least one injection port (22) extending through a wall of the tube to generate at least one radial stream of granular material and conveying gas exiting the lance through said injection port(s) upstream of the discharge opening.

2. The injection lance according to claim 1 , further comprising deflection means configured to promote ejection of granular material through said at least one injection port.

3. The injection lance according to claim 1 or 2, wherein a constriction (24) is arranged within the tube in-between the discharge opening and the staging section, thereby controlling the proportion of granular material discharged through the injection ports.

4. The injection lance according to claim 3, wherein an annular bead (24) defines an orifice of reduced diameter, or said tube has a reduced internal diameter from the discharge opening up to the staging section.

5. The injection lance according to any of the preceding claims, wherein said staging section (20) comprises a plurality of injection ports (22) that extend through the tube wall and are circumferentially distributed therein to generate a plurality of radial streams of granular material and conveying gas exiting the lance through said injection ports upstream of the discharge opening.

6. The injection lance according to claim 5, wherein in said staging section, the injection ports are arranged in one or more planes transversal to the longitudinal axis.

7. The injection lance according to claim 6, wherein each plane comprises between 2 and 15 injection ports.

8. The injection lance according to any of the preceding claims, wherein the constriction is configured to define a staging ratio between 5 wt.% and 75 wt.%, which is defined as the ratio of the granular material mass flow through the injection ports over the total granular material mass flow through the lance.

9. The injection lance according to any of the preceding claims, wherein the ratio of the cumulated flow cross-section through the injection ports over the total flow cross section through the lance, i.e. cumulated flow cross-section though the injection ports and the constriction, lies between 5% and 75%.

10. The injection lance according to any of the preceding claims, further comprising swirl generating features arranged inside and / or outside the tube and extend from the discharge opening to over the staging section, and preferably further beyond.11 . The injection lance according to claim 10, wherein the swirl generating features comprise a helical groove (26) on an interior tube surface; and / or the swirl generating features comprise a helical groove (28) on an external tube surface.

12. The injection lance according to claim 11 , wherein the helical groove has an angle between 5° and 85°, preferably 20° to 60°.

13. The injection lance according to any of the preceding claims, wherein the tube has an inner diameter of between 10 and 100 mm.

14. The injection lance according to any of the preceding claims, wherein the injection ports define a flow cross-section between 5 mm2and 2000 mm2.

15. The injection lance according to any of the preceding claims, wherein said predetermined distance between the discharge opening and injection port is at least 5 mm, preferably between 15 and 150 mm.

16. The injection lance according to any of the preceding claims, wherein two adjacent planes of injection ports are spaced by a distance of between 5 and 100 mm.

17. The injection lance according to any of the preceding claims, wherein said staging section extends over a length of 200 mm.

18. The injection lance according to any of the preceding claims, wherein the injection ports are inclined by 10° to 170° relative to the length axis.

19. The injection lance according to any of the preceding claims, wherein said granular material is selected from pulverized coal, bulk biochar, plastic particles, refuse-derived fuel pellets, or a mixture of two or more thereof.

20. A blast furnace comprising at least one tuyere assembly equipped with an injection lance according to any of the preceding claims, wherein the injection lance is arranged to protrude inside a tuyere or blow pipe of the blast furnace such that the staging section (20) and discharge opening are exposed to the hot blast wind.

21. Use of an injection lance as claimed in any of claims 1 to 19 for injection of granular material into a shaft furnace or blast furnace.

22. Use according to claim 21 , wherein the granular material is selected from pulverized coal, bulk biochar, plastic particles, refuse-derived fuel pellets.

23. A tuyere assembly for a blast furnace, the tuyere assembly defining a hot blast channel therein for carrying hot blast wind, the tuyere assembly equipped with an injection lance according to any of the preceding claims, wherein the injection lance is arranged to protrude inside the hot blast channel such that the staging section (20) and discharge opening are exposed to the hot blast wind.

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