LU102095B1

LU102095B1 - Compact Gas Injection System for a Furnace

Info

Publication number: LU102095B1
Application number: LU102095A
Authority: LU
Inventors: Klaus Peter Kinzel; Gilles Kass; Nicolas Maggioli
Original assignee: Wurth Paul Sa
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2022-03-29

Abstract

The invention concerns a gas injection system for a furnace comprising a furnace wall (12) and a cooling plate (18) wherein the gas injection system comprises a. a gas distribution pipe (14) b. one or more injectors (16) wherein the gas distribution pipe (14) is attached to the furnace wall (12). wherein the injector (16) is installed directly, without any intermediate pieces, in the gas distribution pipe (14) and wherein the injector (16) traverses the furnace wall (12) and the cooling plate (18) and fluidly connects the gas distribution pipe (14) to the furnace. wherein the gas distribution pipe (14) has a D shaped cross section, having a flat side (38) and a rounded side, and wherein the flat side (38) of the D shaped cross section faces the furnace wall (12).

Description

Compact Gas Injection System for a Furnace

[0001] The present invention generally relates to the field of iron metallurgy. The invention more specifically relates to a compact gas distribution and injector system to be fitted to the shaft or stack or to the zone above the belly of an existing blast furnace or shaft furnace or metallurgical furnace.

[0002] With the Paris Agreement and near-global consensus on the need for action on emissions, it is imperative that each industrial sector looks into the development of solutions towards improving energy efficiency and decreasing CO, output.

[0003] One technology developed to reduce the carbon footprint during steel production is the so-called "shaft injection" wherein hot gases (mainly CO and Hz) are injected in the upper part of the blast furnace or shaft furnace or metallurgical furnace, in the part that is generally protected on the inside by cooling plates (cooling elements) or staves or plate coolers or a refractory lining.

[0004] This injection of hot gas in a blast furnace or in a shaft furnace or in a metallurgical furnace at the level of the shaft (shaft injection) is cited in many publications and inventions, but an industrial application has not yet been implemented on a commercial blast furnace.

[0005] One challenge of integrating a shaft injection system on an existing furnace is the limited space availability at the shaft level to incorporate a main gas distribution piping and individual connections to different injection points. The space in this zone of the blast furnace is often congested with cooling pipes, water connections for cooling plates, steel structures, supports, instrumentation, etc. Moreover, maintenance access needs to be assured to these different elements of the blast furnace.

[0006] The object of the present invention is to provide a compact gas distribution and injector system to be fitted to the shaft of an existing blast furnace or shaft furnace or metallurgical furnace.

SUMMARY OF THE INVENTION

[0007] This object is achieved by a system as claimed in claim 1.

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[0008] The present invention relates to a gas injection system for a blast furnace or shaft furnace or metallurgical furnace comprising a furnace wall and a protection element such as a cooling plate or cooling boxes or a refractory lining, wherein the gas injection system comprises a. a gas distribution pipe b. one or more injectors wherein the gas distribution pipe is attached to the furnace wall, wherein the injector is installed directly, without any intermediate pieces, in the gas distribution pipe and wherein the injector traverses the furnace wall and the cooling plate.

wherein the gas distribution pipe has a D shaped cross section and the flat side of the D shaped cross section faces the furnace wall.

[0009] The present invention provides a gas injection system for the injection of a mixture comprising mostly CO and H in a blast furnace or shaft furnace or metallurgical furnace at the level of the cooling plates to further increase productivity, decrease operating costs, reduce coke consumption and CO, emissions in the furnace process.

[0010] The traditional, cumbersome and bulky, multiple connections between the main gas distributor and the injectors are avoided. The absence of multiple connections between the gas distribution pipe and the injectors reduces the potential sources for gas leakage as there are fewer connections and transitions. Indeed, in the present system, the injector is connected directly — without any additional joints or intermediary pieces — to the gas distribution pipe. Gas tightness is particularly important in this application as the hot gas contains CO and Hz, which may spontaneously inflame when leaking to the outside or may form an explosive atmosphere when mixed with air.

[0011] The D shaped cross section of the gas distribution pipe allows installing the gas distribution pipe closer (than with an e.g. round pipe) to the furnace wall and thus use shorter injectors.

[0012] According to an embodiment, the flat side of the D shaped cross section is flush with the furnace wall. This allows using very short injectors and reducing the space needed to install the gas distribution system even further.

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[0013] The flat side of the D shaped cross section may be fixed directly to the furnace wall i.e. by welding or by bolting.

[0014] In an alternative embodiment would be to leave sufficient space for the existing devices and features present on the shell (fixing elements and | instrumentation of the cooling elements

[0015] According to an embodiment, the injector passes through a section of a steel pipe which is connected to the steel shell of the gas distribution pipe and to the furnace wall.

[0016] The gas distribution pipe may further comprise a maintenance and inspection port in an axis of the injector on an opposite side of the gas distribution pipe, i.e. the rounded side.

[0017] in an embodiment, the injector passes through the entire diameter of the gas distribution pipe and has at least one perforation which allows the passage of the gas from the gas distribution pipe through the injector into the furnace.

[0018] The injector may be oriented perpendicular or tangentially to the furnace wall. Preferably, the angle of the injector is between 90° (perpendicular) and 60° (tangential); more preferably, the angle of the injector is between 90° (perpendicular) and 70° (tangential).

[0019] The gas distribution pipe may, depending on the size of the furnace, comprise between 20 and 150 injectors, more preferably between 40 and 80.

[0020] The injectors have a length so that they protrude inside the furnace, or that they are flush with a hot face of the cooling plates or stay slightly in retreat with a hot face of the cooling plates.

[0021] The injectors are preferably cylindrical or conical to match the cylindrical or conical recess made in the staves and the connection pipe to the bustle pipe.

[0022] The gas distribution pipe may be divided in several portions located around the furnace, each portion being supplied by individual hot reducing gas supply lines.

[0023] The invention also concerns a metaliurgic plant for producing iron products, comprising a furnace and at least one gas injection system as described herein.

[0024] The present invention can be implemented with existing equipment well known in the metallurgical field.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawings, wherein Fig.1 is a sectional view of a cooling assembly and a gas injection system with a first preferred embodiment, Fig.2 is a sectional view of a cooling assembly and a gas injection system with a second preferred embodiment Fig. 3 is a sectional view of a cooling assembly and a gas injection system with a third preferred embodiment.

Fig. 4 is a principle diagram of a protective cover for the injector in a) side view and b) front view.

[0026] In the Figures, unless otherwise indicated, same or similar elements are designated by same reference signs.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] The idea of the present invention is to provide a way to combine the gas distribution and injectors such that connecting ducts between the distribution pipe and the injectors are avoided. The compact design of this invention will facilitate the implementation of shaft injection technology in existing furnace environments.

[0028] Figure 1 shows a sectional view of a furnace at the height of the coolers according to a first embodiment.

[0029] On Fig. 1, the blast furnace or shaft furnace or metallurgical furnace wall 12 or shell comprises on the one side (exterior, cold side of the furnace) a gas distribution pipe 14 with an injector 16. eer m sm,

[0030] On the other side (the interior, hot side) of the furnace wall 12, there is a cooling assembly, comprising a cooling plate 18 or stave made of cast iron, copper or a copper alloy. The cooling plate 18 is disposed inside of a furnace wall 12 of the furnace. One surface of the cooling plate 18 (turned towards the hot side of the furnace) comprises a plurality of ribs 20 and grooves 22 to increase the surface area. Also, it could be provided with a refractory lining, which is not shown here for sake of simplicity. A plurality of coolant channels (not shown) are provided in the cooling plate 18.

[0031] The cooling assembly also comprises a plurality of cooling pipes 24, each of which has a pipe channel (not shown) that is connected to a cooling channel (not shown). The cooling pipe 24 can be made of the same material as the cooling plate 18. Each of the cooling pipes 24 passes through a wall opening 26 in the furnace wall 12. The cross-section of the respective wall opening 26 is chosen to be larger than the cross-section of the respective cooling pipe 24 to allow for some movement of the cooling pipe 24 with respect to the furnace wall

12. Such movement may in particular result from a thermally induced deformation of the cooling plate 18, to which the cooling pipes 24 are attached.

[0032] A compensator 28 may be connected to the furnace wall 12 so that it covers the wall openings 26. The hood 28 has a hood opening 30 through which a cooling pipe 24 is passed. The hood 28 may be covering more than one wall opening. Such a hood then comprises more than one hood opening, one for each cooling pipe 24. On an outer side of the hood 28, the cooling pipe 24 is surrounded by a compensator, which is welded to the hood 28 so that it is connected to hood opening 30. The structure of the compensators comprises a cylindrical portion that is connected by welding to the hood 28. A bellows is connected to the cylindrical portion by a ring portion. An annular sleeve portion is connected on the one hand to the bellows and on the other hand to the outside of the cooling pipe. The connection to the cooling pipe 24 is established through an annular first weld. An important feature of the compensator is that the sleeve portion has an inner diameter that increases towards the furnace wall, i.e. it increases from an outer end towards an inner end. in other words, the inside surface of the sleeve portion is not cylindrical but conical. This allows for different angular orientations of the sleeve portion with respect to the cooling pipe 24, while still minimising the distance between the sleeve portion and the cooling pipe 24 at the outer end, where the first weld is applied.

[0033] Fig. 1 also shows a preferred gas injection system comprising a gas distribution pipe 14 and one or more injectors 16.

[0034] The gas distribution pipe 14 comprises a steel shell 32 and an insulation layer 34 made of one or several layers of insulating and dense refractory material. The refractory lining is designed to resist to the high temperature and the composition of the gas circulating in the hollow part 36 of the gas distribution pipe

14. The refractory lining also insulates the steel shell 32 from the hot gases circulating in the hollow space 36 and protects the steel shell 32 of the gas distribution pipe 14 from the high temperature. The insulating effect of the refractory lining allows reducing thermal losses.

[0035] The gas used to inject comprises mainly CO and Hz. Typically the gas has the following composition 20 - 35% v/v CO, 35 - 55 % v/v Hz, 5 - 25% viv N2 , 2 - 5%v/v CO».

[0036] The gas distribution pipe 14 of Fig. 1 has a D shaped cross section wherein the flat side 38 of the D shaped cross section faces the furnace wall 12. It is also possible to use other geometries (rectangular, triangular, hexagonal etc.), as long as there is a flat face facing towards the furnace wall. The injector 16 is integrated into the flat side 38 of the furnace wall 12 and traverses, on the one side, the steel shell 32 and the insulating layer 34 of the gas distribution pipe 14 and, on the other side, the furnace wall 12 and the cooling plate 18.

[0037] The injector 16 is integrated into the gas distribution pipe 14 and connects the gas distribution pipe 14 to the interior of the furnace through the furnace wall 12 and the cooling plate 18. The injector 16 is the only element that fluidly connects the gas distribution pipe 14 to the furnace.

[0038] The absence of multiple connections between the gas distribution pipe 14 and the injectors 16 will also reduce the potential sources for gas leakage as there are fewer connections and transitions. indeed, in the present system, the injector 16 is connected directly — without any additional joints or intermediary

| P-PWU-813/LU 7 LU102095 pieces — to the gas distribution pipe 14. Gas tightness is particularly important in this application as the hot gas contains CO and Hz, which may spontaneously inflame when leaking to the outside or may form an explosive atmosphere when mixed with air.

[0039] In the case shown on Fig. 1, the injector passes through a short section of a steel pipe 42 which is connected to the steel shell 32 of the gas distribution pipe 14 and to the furnace wall 12. This steel pipe 42 enhances the stability of the connection between the gas distribution pipe 14 and the furnace wall 12 and protects the injector 16. The gas distribution pipe 14 is thus at a certain distance from the furnace wall 12. This distance is preferably between 10 and 50 cm.

[0040] The injector 16 is preferably made of a suitable temperature resistant material, like a ceramic material, preferably an oxide ceramic material or a silicon infiltrated silicon carbide material or a nitride based ceramic material. Such materials are chosen to withstand wear caused by the dust laden hot gas and corrosion by the hot reducing gas. The injector 16 may be provided with water cooling.

[0041] The injector 16 is preferably anchored in the insulating layer 34 of the gas distribution pipe 14 with a ring structure 44 that extends perpendicularly to the axis 46 of the injector 16. The ring structure is flush with the inside of the insulation layer 34 of the gas distribution pipe 14.

[0042] On the opposite side of the injector 16, i.e. on the rounded side 40 of the D section, and in the axis of the injector is integrated a maintenance and inspection port 48. The diameter maintenance and inspection port 48 is preferably wide enough to remove the injector 16 when the flange 18 is dismantled. This allows easy dismantling of each injector 16 and easy exchange of the injector 16 in case it is worn out or damaged. The easy dismantling of the injectors 16 is also an advantage for routine inspections of the injecting area inside the furnace during maintenance stops of the furnace. After the injector 16 has been removed, there is an easy access for inspection and possibly cleaning or removal of scaffolds around the injection port 50.

[0043] The injectors 16 can be oriented towards the centre of the furnace or oriented tangentially (not shown). The tangential orientation helps to create a swirl flow in the furnace, which helps increase the distribution of the gas, the mixing with the ascending gas from tuyere level and increases the residence time of the gas in the furnace increasing thus gas utilisation.

[0044] A large number of injectors 16, typically 20 to 80, preferably up to 100 or even up to 150 can be foreseen as the traditional, cumbersome and bulky, multiple connections between the main gas distributor and the injectors are avoided. Installing such a large number of injectors 16 was impossible with the traditional systems due to related congestion of the area outside the furnace. A large number of injectors 16 is beneficial for a good distribution of the hot gas inside the furnace, which is important for an efficient use of the gas in the furnace process.

[0045] When installing a large number of injectors, the diameter of the individual injectors can be quite small. Typically, the inner diameter ranges from 3 - 20 cm, preferably 5 - 10 cm, whereas the outer diameter ranges from 5 - 25 cm, preferably 8 - 15 cm. This allows keeping the openings in the furnace wall and cooling plates 18 small as well, ensuring easy retrofitting of this solution on an | existing furnace without changing the cooling plates.

| [0046] The length of the injectors is adaptable: they can protrude inside the furnace (typically 5 to 10 cm), they can be flush with the hot face of the plates or they can stay slightly in retreat (typically 2 to 10 cm).

[0047] It is also important to note that the gas distribution pipe 14 does not need to be a closed, peripheral collector as for the traditional bustle pipe. If space is not available in a given furnace environment, the gas distribution 14 may be interrupted and a section of the furnace circumference may be devoid of gas distribution pipe and of injectors. The gas distribution pipe 14 can be divided in several portions located around the furnace (e.g. 4 quadrants), each portion being supplied by individual hot reducing gas supply lines (not shown).

[0048] Fig. 2 shows a sectional view of a cooling assembly and a gas injection system with a second preferred embodiment.

[0049] In this particular embodiment the gas distribution pipe 14a is installed flush against the furnace wall 12. The gas distribution pipe 14a may be fixed (welded, bolted, ...) directly onto the furnace wall 12.

[0050] A cooling element 56 such as a channel cooling or a cooling plate can be installed between the steel shell (not shown) of the gas distribution pipe 14a and the furnace wall 12 or between the refractory lining 34 of the gas distribution pipe 14a and the furnace wall 12. The cooling element will protect the furnace wall 12 in addition to the refractory lining 34 from the high temperature of the gas circulating in the hollow space 36. This will limit the risk of local deformation of the shell in case of a failure of the refractory lining.

[0051] This particular embodiment shows a second type of injector 16a with perforations 52, 54 which allow the passage of the gas from the gas distribution pipe 14a into the injector 16a and into the furnace. In this particular case, the injector 16a has two perforations 52, 54. The size and number of these perforations can vary and be adapted to the quantity of gas per hour to be injected into the furnace. The advantage of having an injector 16a which passes through the entire diameter of the gas distribution pipe 14a, is that it can be easily replaced and pulled out in one piece through the maintenance and inspection port 48a.

[0052] Fig. 3 shows a sectional view of a cooling assembly and a gas injection system with a third preferred embodiment.

[0053] In this particular embodiment, the gas distribution pipe 14b is installed flush against the furnace wall 12 as in Fig. 2. The gas distribution pipe | 14b is fixed (welded, bolted, ...) directly onto the furnace wall 12. |

[0054] in this embodiment too, a cooling element 56 such as a channel cooling or a cooling plate is installed between the steel shell (not shown) of the gas distribution pipe 14b and the furnace wall 12 or between the refractory lining 34 of the gas distribution pipe 14b and the furnace wall 12.

[0055] Fig. 3 shows a third type of injector 16b which is dimensioned so as not to protrude into the hollow space 36 of the gas distribution pipe 14b. The injector 16b is flush with the inside of the insulation layer 34 of the gas distribution pipe 14b. Since — contrary to the injector on Fig. 1, — there is no ring structure that | extends perpendicularly to the axis 46 of the injector 16b, the injector 16b can easily be exchanged or replaced through the maintenance and inspection port 48b.

[0056] In the present application, the words “furnace”, "blast furnace", “shaft furnace" and "metallurgical furnace "are interchangeable.

[0057] This D type bustle pipe can be installed vertically to supply one or more row of injector, and arrange on the perimeter of the furnace to match the number of staves and thus prevent interfere with cooling element fixing or instrumentation. The multipie vertical D type bustle pipe are linked together with the supply bustle main.

[0058] In embodiments, a protruding cover may be arranged above the injector(s) and configured to protect the nozzle body front portion that protrudes inside the furnace from a descending burden material. Such protection of the injector nozzle body against abrasion by the descending burden material (sinter/pellets and coke) can e.g. be achieved by means of a steel shell, smooth or corrugated. The principle of this protruding cover 100 is shown in Fig.4 and forms a kind of cap extending in the injector’s longitudinal direction L. it cover the protruding length of the injector (shown in dashed lines) As can be seen, the cover 100 is a curved steel profile section, more particularly having an inverted, rounded V-shape. The apex 100.1 of the V is above the injector 16 and the two branches 100.2 extends on both lateral sides of the injector 16, optionally even below the injector. The cover 100 can be liquid cooled, directly or indirectly. Coolant channels can e.g. be arranged on the lower side of the shell. Reference numerals injection device 26 wall opening 12 furnace wall 28 hood 14, 14a, 14b gas distribution 30 hood opening pipe 32 steel shell of the gas 16, 16a, 16b injector distribution pipe 18 cooling plate 34 insulation layer ribs 36 hollow space 22 grooves 38 flat side 24 cooling pipes 40 rounded side |

42 steel pipe 44 ring structure 46 axis of the injector 48, 48a, 48b maintenance and inspection port 50 Injection port 52, 54 perforations 56 cooling element 100 cover

100.1 apex

100.2 two branches ee,

Claims

1. A gas injection system for a furnace comprising a furnace wall (12) and a cooling plate (18) wherein the gas injection system comprises a. a gas distribution pipe (14) b. one or more injectors (16) wherein the gas distribution pipe (14) is attached to the furnace wall (12), wherein the injector (16) is installed directly, without any intermediate pieces, in the gas distribution pipe (14) and wherein the injector (16) traverses the furnace wall (12) and the cooling plate (18) and fluidly connects the gas distribution pipe (14) to the furnace, wherein the gas distribution pipe (14) has a D shaped cross section, having a flat side (38) and a rounded side, and wherein the flat side (38) of the D shaped cross section faces the furnace wall (12).

2. The gas injection system for a furnace according to claim 1, wherein the flat side (38) of the D shaped cross section is flush with the furnace wall (12).

3. The gas injection system for a furnace according to claim 1 or 2, wherein the flat side (38) of the D shaped cross section is fixed directly to the furnace wall (12).

4. The gas injection system for a furnace according to claim 1, wherein the injector (16) passes through a section of a steel pipe (42) which is connected to the steel shell (32) of the gas distribution pipe (14) and to the furnace wall (12).

5. The gas injection system for a furnace according to any of the preceding claims further comprising a maintenance and inspection port (48, 48a) in an axis of the injector (46) on an opposite side of the gas distribution pipe (14, 14a).

6. The gas injection system for a furnace according to any of the preceding claims wherein the injector (16a) passes through the entire diameter of the gas distribution pipe (14a) and wherein the injector (16a) has at least one perforation (52, 54) which allow the passage of the gas from the gas distribution pipe (14a) through the injector (16a) into the furnace,

7. The gas injection system for a furnace according to any of the preceding claims wherein the injector is oriented perpendicular or tangentially to the furnace wall.

8. The gas injection system for a furnace according to any of the preceding claims wherein the gas distribution pipe comprise between 20 and 40 injectors.

9. The gas injection system for a furnace according to any of the preceding claims wherein the injectors have an adaptable length so that they either protrude inside the furnace, or that they are flush with a hot face of the cooling plates or stay slightly in retreat with a hot face of the cooling plates.

10. The gas injection system for a furnace according to any of the preceding claims wherein the gas distribution pipe (14) is divided in several portions located around the furnace, each portion being supplied by individual hot reducing gas supply lines.

11. The gas injection system for a furnace according to any one of the preceding claims, wherein a protruding cover (100) is arranged above the injector(s) and configured to protect the nozzle body front portion that protrudes inside the furnace from a descending burden material.

12. A metallurgic plant for producing iron products, comprising a furnace and at least gas injection system according to any of the preceding claims.

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