EP-4735648-A1 - DOUBLE WALL LANCE FOR INJECTING REDUCING AGENT AND OXYGEN THROUGH A TUYERE IN A BLAST FURNACE

EP4735648A1EP 4735648 A1EP4735648 A1EP 4735648A1EP-4735648-A1

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.

Inventors

DOMINGO, Pascale
VERVISCH, Luc
BARNAUD, Camille
DODIER, Eric
GHAZAL, Ghassan
NGUYEN, Phuc Danh
SERT, DOMINIQUE

Assignees

ArcelorMittal
Centre National de la Recherche Scientifique (CNRS)
Institut National des Sciences Appliquées de Rouen (INSA)
Universite de Rouen Normandie

Dates

Publication Date: 20260506
Application Date: 20230629

Claims (1)

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.

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 t