EP4735648A1 - Double wall lance for injecting reducing agent and oxygen through a tuyere in a blast furnace - Google Patents

Double wall lance for injecting reducing agent and oxygen through a tuyere in a blast furnace

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Publication number
EP4735648A1
EP4735648A1 EP23741478.4A EP23741478A EP4735648A1 EP 4735648 A1 EP4735648 A1 EP 4735648A1 EP 23741478 A EP23741478 A EP 23741478A EP 4735648 A1 EP4735648 A1 EP 4735648A1
Authority
EP
European Patent Office
Prior art keywords
front face
lance
cap
outlet holes
reducing agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23741478.4A
Other languages
German (de)
French (fr)
Inventor
Pascale DOMINGO
Luc VERVISCH
Camille BARNAUD
Eric DODIER
Ghassan GHAZAL
Phuc Danh NGUYEN
Dominique Sert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Centre National de la Recherche Scientifique CNRS
Universite de Rouen
Institut National des Sciences Appliquees de Rouen
ArcelorMittal SA
Original Assignee
Centre National de la Recherche Scientifique CNRS
Universite de Rouen
Institut National des Sciences Appliquees de Rouen
ArcelorMittal SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Centre National de la Recherche Scientifique CNRS, Universite de Rouen, Institut National des Sciences Appliquees de Rouen, ArcelorMittal SA filed Critical Centre National de la Recherche Scientifique CNRS
Publication of EP4735648A1 publication Critical patent/EP4735648A1/en
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B7/00—Blast furnaces
    • C21B7/16—Tuyéres
    • C21B7/163—Blowpipe assembly
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B1/00—Shaft or like vertical or substantially vertical furnaces
    • F27B1/10—Details, accessories or equipment specially adapted for furnaces of these types
    • F27B1/16—Arrangements of tuyeres
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/16—Introducing a fluid jet or current into the charge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/16—Introducing a fluid jet or current into the charge
    • F27D2003/168—Introducing a fluid jet or current into the charge through a lance
    • F27D2003/169—Construction of the lance, e.g. lances for injecting particles

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Blast Furnaces (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

The invention relates to a double wall lance for injecting reducing agent and oxygen through a tuyere comprising: a. an inner tube (5) for injecting reducing agent (2), b. an outer tube (6) for injecting oxygen (3) which surrounds the inner tube (5), c. an end part (7, 7a,7b,7c) closing the lance (1) and having: - a front face (11a,11b,11c) having a diameter D and comprising: i. a reducing agent outlet hole (8a,8b,8c), ii. a front face periphery (9a,9b,9c) comprising a plurality of main oxygen outlet holes (10a,10b,10c), - a cap (12a,12b,12c) surrounding the end part (7,7a,7b,7c) and extending over a length L starting from the front face (11a,11b,11c) of the end part (7, 7a,7b,7c) to a free end edge (14a,14b,14c), wherein the length L of the cap (12a,12b,12c) represents more than 21,3% of the diameter D of the front face (11a,11b,11c). The invention also relates to a method to inject hot reducing gas into a blast furnace through a tuyere (4) using such double wall lance.

Description

Double wall lance for injecting reducing agent and oxygen through a tuyere in a blast furnace
[001 ] The invention is related to a double wall lance for injecting reducing agent and oxygen through a tuyere and to a method for injecting hot reducing gas through a tuyere into a blast furnace.
[002] In a blast furnace, a blast, also called hot blast as it has usually a temperature over 900°C, is injected through a tuyere into the blast furnace. Prior to this injection, the blast furnace has been charged with raw materials necessary for pig iron production, such as coke, briquettes, pellets, iron ore, sintered iron... Coke is charged into the blast furnace as the main reducing agent. The ferrous burden will progressively heat-up and be reduced into iron in the shaft of the furnace. It will finally soften and be melted in the lower part of the furnace, forming a so-called cohesive zone there. Below this level, coke will remain the only solid material in the lower furnace (coke reserve zone) and in the hearth of the blast furnace. Pulverized coal (PC), is generally considered as the main auxiliary reducing agent. It is injected into the blast furnace thanks to a sub-lance introduced into the tuyere. The injection of the blast together with the PC particles into the coke reserve zone creates a void zone called raceway in front of the tuyeres due to the partial combustion of the reducing agents with the oxygen of the blast. The size of this cavity is linked to several parameters and among them, the impulse of the gas jet at the exit of the tuyere. This impulsion can be expressed as such: I (N) = Qm (kg/s) x V (m/s), wherein I is the impulsion, Qm is the mass flow rate of the gas exiting the tuyere and V is the speed of the gas. In a standard way of operating the blast furnace this impulsion is around 700 N.
[003] In the last decades, efforts have been made to reduce carbon dioxide emissions at the blast furnace level. One of the developed solutions, named TGRBF for Top Gas Recycling Blast Furnace, which is described in patent application WO 2010/106387, consists in treating the gas exhausted from the blast furnace and re-injecting at least a part of the resulting reducing gas in the blast furnace, through the classical tuyeres located at the top of the hearth of the furnace. Compared to the “classical” operation method of the blast furnace, and in the currently preferred version of this new type of operation, the difference consists in replacing all the hot blast by the recycled reducing gas. However, in this configuration the specific consumption of the recycled reducing gas is significantly lower than the specific consumption of hot blast in classical operation, with also potentially a lower temperature. This results in a lower velocity of the gas stream at tuyere outlet compared to the classical hot blast operation, corresponding to stream impulse significantly lower than before and especially below 300 N.
[004] Consequently, its injection into the blast furnace creates a smaller raceway. The size of the raceway is of importance because it has an impact on the gas distribution in the lower furnace, on the heat load on the furnace wall which might be critical in this high temperature zone of the furnace. It also impacts the efficiency of the partial combustion of the reducing agent like pulverized coal injected through the tuyeres, giving the possibility to unburnt particles to accumulate in the lower furnace and to disturb its permeability. The melting conditions at the cohesive zone level might also be affected.
[005] There is then a need for a device which allows to increase the size of the raceway created when injecting hot reducing gas at the normal tuyeres when the blast furnace is operated in TGR-BF mode while preserving the sub-lance material from unacceptable high temperatures.
[006] This problem is solved by the double wall lance of the invention, comprising a. an inner tube for injecting reducing agent, b. an outer tube for injecting oxygen which surrounds the inner tube, c. an end part located at the exit of the lance within the tuyere, said end part closing the lance and having: a front face having a diameter D and comprising: i. a reducing agent outlet hole located in front of the inner tube so as to allow reducing agent exit, a front face periphery comprising a plurality of main oxygen outlet holes located in front of the outer tube to allow oxygen exit, a cap with an open end and an annular wall surrounding the end part and extending over a length L starting from the front face of the end part to a free end edge, wherein the length L of the cap end (12a, 12b, 12c) represents more than 21 ,3% of the diameter D of the front face (11 a, 11 b, 11 c). [007] The lance of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations:
- the cap extends over a length L greater than 12 mm starting from the front face of the end part to a free end edge.
- the cap extends over a length L of at least 13 mm starting from the front face of the end part to a free end edge.
- the total surface of the main oxygen outlet holes represents at least 30% of the surface of the front face periphery of the front face of the end part of the lance,
- the walls of the inner tube are made of solid material,
- the main oxygen outlet holes are spaced along the front face periphery,
- the main oxygen outlet holes are at least seven in number,
- the main oxygen outlet holes have a trapezoidal shape,
- the front face periphery further comprises secondary oxygen outlet holes located between the main oxygen outlet holes around the periphery of the front face periphery,
- the total surface of the secondary oxygen outlet holes represents at most 10% of the surface of the front face periphery of the front face of the end part of the lance,
- the reducing agent outlet hole is located in the same transversal plane as the free end edge of the cap or is extending beyond the free end edge of the cap,
- according to a preferred embodiment of the invention: i. the front face periphery is arranged perpendicularly to the annular wall of the cap, ii. the reducing agent outlet hole is extending beyond the free end edge of the cap, iii. the front face periphery comprises seven main oxygen outlet holes, and iv. the secondary oxygen outlet holes have a stadium shape.
- alternatively, the front face periphery is arranged convergently towards the open end of the cap and the reducing agent outlet hole is located in the same transversal plane as the free end part of the cap, - according to another preferred embodiment of the invention including such convergently arrangement, the front face periphery comprises eight main oxygen outlet holes, and the secondary oxygen outlet holes have a circular shape,
- according to another preferred embodiment of the invention also including such convergently arrangement, the front face periphery comprises seven main oxygen outlet holes, and the secondary oxygen outlet holes have a stadium shape.
[008] The invention also concerns a method to inject hot reducing gas into a blast furnace through a tuyere, said method comprising: a. injecting hot reducing gas into a tuyere, b. injecting reducing agent in the inner tube of a double wall lance as previously indicated, said double wall lance being inserted into the tuyere, c. injecting an oxygen-carrying gas in the outer tube of the double wall lance, and d. contacting oxygen-carrying gas with the reducing agent before its injection into to the blast furnace.
[009] Preferably, the hot reducing gas comprises recycled top gas of the blast furnace.
[0010] Other characteristics and advantages of the invention will emerge clearly from the description of it that is given below by way of an indication, and which is in no way restrictive, with reference to the appended figures in which:
Figure 1 is a general cross-sectional view of the double wall lance of the invention located in the tuyere;
Figure 2 is a perspective view of the end part of a first embodiment of the double wall lance of the invention;
Figure 3 is a front view of the end part of the double wall lance of Figure 2;
Figure 4 illustrates the trajectory of coal particles inside the tuyere when using the double wall lance of Figure 2;
Figure 5 is a perspective view of the end part of a second embodiment of the double wall lance of the invention;
Figure 6 is a front view of the end part of the double wall lance of Figure 5; Figure 7 is a cross section view of the end part of the double wall lance of Figure 5;
Figure 8 illustrates the trajectory of coal particles inside the tuyere when using the double wall lance of Figure 5;
Figure 9 is a perspective view of the end part of a third embodiment of the double wall lance of the invention;
Figure 10 is a front view of the end part of the double wall lance of Figure 9;
Figure 11 illustrates the trajectory of coal particles inside the tuyere when using the double wall lance of Figure 9;
[0011 ] Elements in the figures are illustration and may not have been drawn to scale.
[0012] With reference to figure 1 , the lance 1 of the invention is obliquely introduced into the tuyere 4, this tuyere 4 having an end part 16 and an outlet hole 17 to allow injection of a hot gas into the blast furnace. The end part 7 of the lance 1 is located into the end part 16 of the tuyere 4 upstream of the outlet hole 17. The hot gas 18 which flows through the tuyere 6 has a temperature from 700 to 1300°C and can be a recycled top gas. This recycled gas contains preferentially more than 70 % CO/H2 mixture, more preferentially over 80 % and ideally more than 90 %, with a mixture of CO2/H2O limited to less than 5 %, and preferentially less than 3 %, remainder being mainly nitrogen N2
[0013] The lance 1 of the invention comprises an inner tube 5 for reducing agent and an outer tube 6 which surrounds the inner tube 5 thus defining an annular tube through which oxygen flows. The reducing agent may be natural gas, coking gas, fuel-oil or pulverized coal. Preferably, the reducing agent is pulverized coal. The axis of the end part 7 of the double wall lance 1 is slightly inclined to inject reducing agent 2 and oxygen 3 into the hot gas 18 along the longitudinal axis XX’ of the tuyere 4. [0014] The resulting exothermic combustion reaction between the reducing agent and oxygen occurs close to the outlet of the lance 1 due to the injection of oxygen, which leads to an increase of the impulse force of the gas jet at the outlet 17 of the tuyere 4. The temperature of the flame can reach almost 3000°C at some locations, while a temperature higher than 1100°C at the end part 7 of the lance 1 can cause irreversible damage to the lance 1 . [0015] According to the invention, the end part 7 of the lance 1 has a front face having a diameter D and comprising the reducing agent outlet hole and a front face periphery comprising a plurality of main oxygen outlet holes which surround the reducing agent outlet hole. In combination which such an arrangement of the oxygen outlet holes, the end part 7 of the lance 1 comprises a cap surrounding this end part 7 and extending over a length L of starting from the front face of the end part. According to the invention, the length L of the cap represents more than 21 ,3% of the diameter D of the front face. Preferably, the length L is more than 12 mm and more preferably of at least 13 mm. Such minimum length of the cap has been discovered as allowing to avoid hot spots greater than 1100°C at the end part 7 of the lance 1 .
[0016] The minimum length of the cap must be considered in conjunction with the arrangement and the surface of the oxygen outlet holes since the oxygen outlet holes contribute directly to the combustion and therefore to an increase of the temperature near the lance, while increasing the length of the cap leads to decrease the temperature near the lance.
[0017] Advantageously, the total surface of the main oxygen outlet holes represents at least 30% of the surface of the front face periphery of the front face the end part of the lance thus allowing to inject the required amount of oxygen to obtain an acceptable combustion force. Preferably, the total surface of the main oxygen outlet holes is not more than 60% of the surface of the front face periphery.
[0018] More advantageously, the front face periphery further comprises a plurality of secondary oxygen outlet holes located between the main oxygen outlet holes. Preferably, the total surface of the secondary oxygen outlet holes represents no more than 10% of the surface of the front face periphery of the front face of the end part of the lance and is more preferably comprised between 3 to 10% of the surface of the front face periphery.
[0019] Advantageously, the end part of the cap is circular to avoid the formation of heat sticking points.
[0020] In order to locate the combustion close to the exit of the lance 1 , the wall of the inner tube 5 is made of solid material so as to avoid any damage along the inner tube 5. [0021 ] Moreover, in order to uniformly distribute the oxygen flow gas in the tuyere, the main oxygen outlet holes are spaced along the periphery of the front face. Such an arrangement results in a homogeneous temperature distribution in the tuyere 4. The main oxygen outlet holes can be uniformly spaced along the periphery of the front face but advantageously, the main oxygen outlet holes are unregularly spaced along the periphery of the front face in order to avoid disturbances coming from vibrations.
[0022] To optimise the contact between oxygen and the reducing gas downstream the tip of the lance, hence the combustion of the reducing gas, the main oxygen outlet holes are at least seven in number. In the examples described later, the front face periphery comprises seven or eight main oxygen outlet holes.
[0023] The shape of the main oxygen outlet holes is also defined to both optimize the combustion reaction and to maintain the combustion force at an acceptable level. For this purpose, the main oxygen outlet holes have a trapezoidal shape, the greatest width being on the side of the annular wall of the cap.
[0024] In the context of the invention, it has been discovered that the addition of secondary oxygen outlet holes located between the main oxygen outlet holes allows to limit the recirculation of the gas (in particular CO) inside the cap thus further reducing the temperature and hot spots at the end part 7 of the lance 1. For this purpose, the total surface of the secondary oxygen outlet holes represents between 3 to 10 % of the surface of the front face. The secondary oxygen outlet holes can have circular shape or stadium shape. The shape of the secondary oxygen outlet holes must be adjusted according to the other structural parameters of the lance.
[0025] Another technical feature of the lance of the present invention is the relative position of the reducing agent outlet hole to the free end edge of the cap. In this regard, it has been found that to avoid recirculation of coal particles within the cap, the reducing agent outlet hole should either be in the same transverse plane as the free end edge of the cap or should extend beyond the free end edge of the cap.
[0026] The shape of the front face periphery through which the oxygen is injected can be adjusted to optimize the efficiency of the injection through the tuyere. For this purpose, the front face periphery can be either perpendicular to the annular wall of the cap or can be arranged convergently towards the open end of the cap. In both configurations, the relative position of the reducing agent outlet hole to the free end edge of the cap is adjusted according to the chosen shape option.
[0027] The invention is also related to a method to inject hot reducing gas into a blast furnace through a tuyere using the above-described double lance. The method comprises the following steps: injecting hot reducing gas into a tuyere, injecting reducing agent in the inner tube of the double wall lance, which is inserted into the tuyere, injecting an oxygen-carrying gas in the outer tube of the double wall lance, and contacting oxygen-carrying gas with the reducing agent before its injection into the blast furnace.
[0028] The hot reducing gas advantageously comprises a recycled top gas of the blast furnace for environmental considerations.
[0029] Three preferred embodiments of a lance 1 according to the invention are described below.
[0030] In the first embodiment of the lance of the invention illustrated on figures 2 to 4, the end part 7a of the double wall lance 1 a has a front face 11 a having a diameter D of 56,5 mm and comprising the circular reducing agent outlet hole 8a forming free end of the inner tube 5. Said circular reducing agent outlet hole 8a is surrounded by a front face periphery 9a located between the inner tube 5 and the outer tube 6. The end part 7a of the lance 1 a is slightly inclined to inject reducing agent 2 and oxygen 3 into the gas 18 along the longitudinal axis XX’ of the tuyere 4 (figure 1 ).
[0031 ] The end part 7a further comprises a cap 12a made of an annular wall 13a which is substantially truncated cone-shaped. The cap 12a extends from the front face 11 a to a circular free end edge 14a. The cap has a length of 16 millimetres so that the length of the cap represents 28,3% of the diameter of the front face.
[0032] The front face periphery 9a is arranged perpendicularly to the annular wall 13a of the cap and comprises seven main oxygen outlet holes 10a uniformly spaced along the front face periphery 9a and having a trapezoidal shape, the greatest width being on the side of the annular wall 13a of the cap 12a. Total surface of the seven main oxygen outlet holes 10a represents about 36% of the surface of the front face periphery 9a of the front face 11 a of the end part 7a of the lance 1 a. [0033] The front face periphery 9a further comprises seven secondary oxygen outlet holes 15a each being located between two adjacent main oxygen outlet holes 10a on the side of the annular wall 13a of the cap 12a. Each secondary oxygen outlet holes 15a has a stadium shape. Total surface of the secondary oxygen outlet holes 15a represents about 6% of the surface of the front face periphery 9a of the front face 11 a of the end part 7a of the lance 1 a.
[0034] The reducing agent outlet hole 8a extends beyond the front face periphery 9a and also beyond the free end edge 14a of the cap 12a. The outer extending part of the inner tube 5 is of 20 millimetres so that the reducing agent outlet hole 8a extends beyond the free end edge 14a of the cap 12a of 4 millimetres.
[0035] Thanks to such configuration, the maximum temperature of the end part 7a of the lance 1 a is of 1 030°C and the impulse force of the gas flow at the outlet of the tuyere is of 384N.
[0036] Referring to figure 4, the coal particles 2 are not sucked into the cap 12a and are ejected from the tuyere 4 without hitting the inner wall of the tuyere 4.
[0037] In the second embodiment of a lance according to the invention illustrated in figures 5 to 8, the end part 7b of the double wall lance 1 b has a front face 11 b having a diameter D of 56,5 mm and comprising the circular reducing agent outlet hole 8b forming free end of the inner tube 5. Said circular reducing agent outlet hole 8b is surrounded by a front face periphery 9b located between the inner tube 5 and the outer tube 6. As shown in Figure 7, the end part 7b of the lance 1 b is slightly inclined to inject reducing agent 2 and oxygen 3 into the gas 18 along the longitudinal axis XX’ of the tuyere 4 (figure 1 ).
[0038] The end part 7b further comprises a cap 12b made of an annular wall 13a which is slightly truncated cone-shaped (figure 7). The cap 12b extends from the front face 11 b to a circular free end edge 14b. The cap 12b has a length L of 16 millimetres so that the length of the cap represents 28,3% of the diameter D of the front face.
[0039] The front face periphery 9b is arranged convergently towards the open end of the cap 12b and up to free end edge 14b of the cap 12b so that the reducing agent outlet hole 8b is located in the same transversal plane as the free end edge 14b of the cap 12b (figure 7). The angle of convergence is of 28°. [0040] The front face periphery 9b comprises eight main oxygen outlet holes 10b unregularly spaced along the front face periphery 9b and having a trapezoidal shape, the greatest width being on the side of the annular wall 13b of the cap 12b. Total surface of the eight main oxygen outlet holes 10b represents about 36% of the surface of the front face 11 b of the end part 7b of the lance 1 b.
[0041 ] The front face periphery 9b further comprises secondary oxygen outlet holes 15b located between the main oxygen outlet holes 10b. Each secondary oxygen outlet holes 15b has a circular shape. One, two or three secondary oxygen outlet holes 15b are located between two adjacent main oxygen outlet holes 10b on the side of the annular wall 13b of the cap 12b then leading to the unregularly arrangement of the main oxygen outlet holes 10b.
[0042] Total surface of the secondary oxygen outlet holes 15b represents about 6% of the surface of the front face periphery 9b of the front face 11 b of the end part 7b of the lance 1 b.
[0043] Thanks to such configuration, the maximum temperature of the end part 7b of the lance 1 b is lower than 1 100°C and the impulse force is of 366N.
[0044] Referring to figure 8, the coal particles 2 are not sucked into the cap 12b and are ejected from the tuyere 4 without hitting the inner wall of the tuyere 4.
[0045] In the third embodiment of a lance according to the invention illustrated in figures 9 to 11 , the end part 7c of the double wall lance 1 c has a front face 11 c having a diameter D of 56,5 mm and comprising the circular reducing agent outlet hole 8c forming free end of the inner tube 5. Said circular reducing agent outlet hole 8c is surrounded by a front face periphery 9c located between the inner tube 5 and the outer tube 6. As in the first and second embodiments, the end part 7c of the lance 1 c is slightly inclined.
[0046] The end part 7c further comprises a cap 12c made of an annular wall 13c which is slightly truncated cone-shaped. The cap 12c extends from the front face 11 c to a circular free end edge 14c. The cap 12c has a length L of 16 millimetres so that the length of the cap represents 28,3% of the diameter D of the front face.
[0047] The front face periphery 9c is arranged convergently towards the open end of the cap 12c and up to free end edge 14c of the cap 12c so that the reducing agent outlet hole 8b is located in the same transversal plane as the free end edge 14c of the cap 12c. The convergence angle is of 42°.
[0048] The front face periphery 9c comprises seven main oxygen outlet holes 10c uniformly spaced along the front face periphery 9c and having a trapezoidal shape, the greatest width being on the side of the annular wall 13c of the cap 12c.
[0049]
[0050] The front face periphery 9c further comprises seven secondary oxygen outlet holes 15c each being located between two adjacent main oxygen outlet holes 10c on the side of the annular wall 13c of the cap 12c. Each secondary oxygen outlet holes 15c has a stadium shape.
[0051 ] In this embodiment, the surface of each main oxygen outlet holes 10c is of 87,94 mm2 and the surface of each secondary oxygen outlet holes 15c is of 14,57 mm2. Therefore, for a total surface of the front face periphery 9c of 1 688,80 mm2, the total surface of the seven main oxygen outlet holes 10c represents 36,45% of the surface of the front face periphery 9c and the total surface of the seven secondary oxygen outlet holes 15c represents 6,04% of the surface of the front face periphery 9c. The total surface of the main oxygen outlet holes 10c and of the secondary oxygen outlet holes 15c thus represents 42,09% of the surface of the front face periphery 9c.
[0052] Thanks to such a configuration, the maximum temperature of the end part 7b of the lance 1 b is lower than 1 100°C and the impulse force is of 366N.
[0053] Referring to figure 11 , the coal particles 2 are not sucked into the cap 12c and are ejected from the tuyere 4 without hitting the inner wall of the tuyere 4.
[0054] Comparative examples demonstrating the effect of the features of the lance of the invention will now be described.
[0055] Tables 1 and 2 show the results obtained with lances according to the invention compared to lances outside of the scope of the invention.
[0056] Three results are presented in these tables (last three columns): the impulse force, expressed in Newton, the reducing agent particle trajectory in the tuyere and the absence or presence of hot spots at the end part of the lance.
[0057] For the reducing agent particle trajectory, signs indicate that coal particles hit the inner wall of the tuyere while the signs “++” indicate that coal particles do not hit the inner wall of the tuyere. Sign means that the trajectory of the particles is acceptable.
[0058] Concerning the hot spots at the end part of the lance, signs mean that the temperature at the end part of the lance is unacceptably upper than 1 100°C while the signs “++” mean that the temperature at the end part of the lance is lower than 1 100°C. The sign “+” means that the temperature at the end part of the lance is an allowable range around 1 100°C while being lower than 1 100°C.
[0059] In Table 1 , examples A to E correspond to lances which are not according to the invention. In Tables 1 and 2, examples 1 to 7 correspond to lances according to the invention. Examples 1 to 3 respectively correspond to embodiments 1 to 3 previously described in reference to figures 2 to 11 . In all the examples A to E and 1 to 7, the diameter of the front face is of 56,5 mm.
[0060] According to Table 1 , when the length of the cap is of 12 mm (representing 21 ,3% of the diameter of the front face), the temperature at the end part of the lance is unacceptable while for a length of the cap of 13mm (representing 23,0% of the diameter of the front face), the temperature is in an allowable range around 1 100°C. Therefore, the length of the cap has to be greater than 21 ,3% of the diameter of the front face and has thus to be greater than 12mm and more preferably of at least of 13mm.
[0061 ] Table 1 illustrates the effect of the presence of the cap and also of the length of the cap. In order to reach an allowable temperature at the end part of the lance, the length of the cap has to represent at least 23% of the diameter of the front face. In these examples, the length of the cap must be of at least 13 millimetres. A length of 16 millimetres is preferred (according to Examples 1 to 3) to reach a temperature lower than 1 100 °C.
[0062] Table 2 illustrates the results obtained for four examples of a lance according to the invention for which the front face periphery is perpendicular to the wall of the cap. Example 1 previously described in reference to figure 2 to 4 gives the best results.
Table 1 : Comparative examples showing the effect of the cap and of the length of the cap
Table 2: Comparative examples of the invention for a perpendicular shape of the front face periphery

Claims

1 ) A double wall lance (1 ) for injecting reducing agent (2) and oxygen (3) through a tuyere (4) of a blast furnace, said lance (1 , 1 a, 1 b, 1 c) comprising: a. an inner tube (5) for injecting reducing agent (2), b. an outer tube (6) for injecting oxygen (3) which surrounds the inner tube (5), c. an end part (7, 7a, 7b, 7c) located at the end of the lance (1 ) within the tuyere (4), said end part (7, 7a, 7b, 7c) closing the lance (1 ) and having:
- a front face (11 a, 11 b, 11 c) having a diameter D and comprising: i. a reducing agent outlet hole (8a, 8b, 8c) located in front of the inner tube (5) so as to allow reducing agent (2) exit, ii. a front face periphery (9a, 9b, 9c) comprising a plurality of main oxygen outlet holes (10a, 10b, 10c) located in front of the outer tube (6) to allow oxygen (3) exit,
- a cap (12a, 12b, 12c) with an open end and an annular wall (13a, 13b, 13c) surrounding the end part (7, 7a, 7b, 7c), extending over a length L starting from the front face (11 a, 11 b, 11 c) of the end part (7, 7a, 7b, 7c) to a free end edge (14a, 14b, 14c) wherein the length L of the cap (12a, 12b, 12c) represents more than 21 ,3% of the diameter D of the front face (11 a,11 b,11 c).
2) A lance according to claim 1 , wherein the cap (12a, 12b, 12c) extends over a length L greater than 12 mm starting from the front face (11 a, 11 b, 1 1c) of the end part (7, 7a, 7b, 7c) to a free end edge (14a, 14b, 14c).
3) A lance according to anyone of claims 1 and 2, wherein the cap (12a, 12b, 12c) extends over a length L of at least 13 mm starting from the front face (11 a, 11 b, 1 1c) of the end part (7, 7a, 7b, 7c) to a free end edge (14a, 14b, 14c).
4) A lance according to anyone of claims 1 or 2, wherein total surface of the main oxygen outlet holes (10a, 10b, 10c) represents at least 30% of the surface of the front face periphery (9a, 9b, 9c) of the front face (11a, 11 b, 11 c) of the end part (7, 7a, 7b, 7c) of the lance (1 , 1 a, 1 b, 1c). 5) A lance according to anyone of claims 1 to 4, wherein the walls of the inner tube (5) is made of solid material.
6) A lance according to anyone of the previous claims wherein the main oxygen outlet holes (10a, 10b, 10c) are spaced along the front face periphery (9a, 9b, 9c).
7) A lance according to anyone of the previous claims wherein the main oxygen outlet holes (10a, 10b, 10c) are at least seven in number.
8) A lance according to anyone of the previous claims wherein the main oxygen outlet holes (10a, 10b, 10c) have a trapezoidal shape.
9) A lance according to anyone of the previous claims wherein the front face periphery (9a, 9b, 9c) further comprises secondary oxygen outlet holes (15a, 15b, 15c) located between the main oxygen outlet holes (10a, 10b, 10c) around the periphery of the front face periphery (9a, 9b, 9c),
10) A lance according to claim 9 wherein the total surface of the secondary oxygen outlet holes (15a, 15b, 15c) represents at most 10% of the surface of the front face periphery (9a, 9b, 9c) of the front face (11 a, 11 b, 11 c) of the end part (7, 7a, 7b, 7c) of the lance (1 , 1 a, 1 b, 1 c).
11 ) A lance according to claim 10 wherein the reducing agent outlet hole (8a, 8b, 8c) is located in the same transversal plane as the free end edge (14a, 14b, 14c) of the cap (12a, 12b, 12c) or is extending beyond the free end edge (14a, 14b, 14c) of the cap (12a, 12b, 12c).
12) A lance according to claim 11 wherein:
- the front face periphery (9a) is arranged perpendicularly to the annular wall (13a) of the cap (12a),
- the reducing agent outlet hole (8a) is extending beyond the free end edge (14a) of the cap (12a),
- the front face periphery (9a) comprises seven main oxygen outlet holes (10a), and
- the secondary oxygen outlet holes (15a) have a stadium shape. 13) A lance according to claim 11 wherein the front face periphery (9b, 9c) is arranged convergently towards the open end of the cap (12b, 12c) and wherein the reducing agent outlet hole (8b, 8c) is located in the same transversal plane as the free end part (14b, 14c) of the cap (12b, 12c).
14) A lance according to claim 13 wherein the front face periphery (9b) comprises eight main oxygen outlet holes (10b), and wherein the secondary oxygen outlet holes (15b) have a circular shape.
15) A lance according to claim 13 wherein the front face periphery (9c) comprises seven main oxygen outlet holes (10c), and wherein the secondary oxygen outlet holes (15c) have a stadium shape.
16) A method to inject hot reducing gas into a blast furnace through a tuyere (4), said method comprising: a. injecting hot reducing gas into a tuyere (4), b. injecting reducing agent (2) in the inner tube (5) of a double wall lance (1 , 1 a, 1 b, 1 c) according to anyone of the previous claims, said double wall lance (1 , 1 a, 1 b, 1 c) being inserted into the tuyere (4), c. injecting an oxygen-carrying gas (3) in the outer tube (6) of the double wall lance (1 , 1 a, 1 b, 1 c), and d. contacting oxygen-carrying gas (3) with the reducing agent (2) before its injection into to the blast furnace.
17) A method according to claim 16 wherein the hot reducing gas comprises recycled top gas of the blast furnace.
EP23741478.4A 2023-06-29 2023-06-29 Double wall lance for injecting reducing agent and oxygen through a tuyere in a blast furnace Pending EP4735648A1 (en)

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US20070205543A1 (en) * 2006-03-06 2007-09-06 Lanyi Michael D Oxidant-swirled fossil fuel injector for a shaft furnace
US8992664B2 (en) 2009-03-17 2015-03-31 ArcelorMittal Investigación y Desarrollo, S.L. Blast furnace top gas recycling process and corresponding recycling equipment
AU2011326369B2 (en) * 2010-11-10 2017-06-08 Berry Metal Company Reinforced distributor for post-combustion lance
WO2019099951A1 (en) * 2017-11-16 2019-05-23 Berry Metal Company Fluid cooled housing system for instruments of a metal making furnace
KR102846480B1 (en) * 2020-05-15 2025-08-13 제이에프이 스틸 가부시키가이샤 Therefore, the method of operation

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