AU2010251491B2

AU2010251491B2 - Metallurgical melting and treatment unit

Info

Publication number: AU2010251491B2
Application number: AU2010251491A
Authority: AU
Inventors: Bernhard Handle; Bojan Zivanovic
Original assignee: Refractory Intellectual Property GmbH and Co KG
Current assignee: Refractory Intellectual Property GmbH and Co KG
Priority date: 2009-05-20
Filing date: 2010-04-22
Publication date: 2013-01-31
Anticipated expiration: 2030-04-22
Also published as: PL2253916T3; WO2010133283A1; CA2760352C; JP5421455B2; ES2357684T3; AU2010251491A1; CN102428335B; EP2253916A1; ATE496267T1; PE20121144A1; CN102428335A; BRPI1011059A2; CA2760352A1; EP2253916B1; KR20120024577A; CL2011002867A1; DE502009000332D1; JP2012527595A; KR101322572B1

Abstract

The invention relates to a metallurgical melting and treatment unit, in particular a substantially cylindrical vessel for holding and treating a nonferrous metal bath.

Description

- 1 Metallurgical melting and processing unit Description The invention relates to a metallurgical melting and processing unit, in particular an essentially cylindrical vessel for accommodating and processing a non ferrous metal melt. These metallurgical units/vessels include the following in particular: Peirce-Smith converters, Teniente converters, Noranda reactors, copper refining furnaces. The basic design of such units for melting metals and for accommodating and processing metal melts is as follows: - The vessel/furnace is of an essentially cylindrical shape and the longitudinal axis of the cylinder extends essentially horizontally when the vessel is in the operating position. This is illustrated in Figure 1 in the case of a Peirce-Smith converter. - The vessel has an outer metal casing and an inner refractory lining. - The vessel is provided with several nozzles which run from outside through the metal casing of the furnace and through the inner refractory lining into the actual furnace space, to enable a processing gas such as air to be injected into the metal melt. - In this connection, the nozzles respectively the nozzle openings are disposed adjacent to one another - 2 spaced at a distance apart in the longitudinal direction of the longitudinal axis of the vessel. In other words, the nozzles are disposed along a line of the cylindrical casing, the line extending parallel to the cylinder axis. The axis of the nozzles usually extends in a plane perpendicular to the cylinder axis. - Up to a hundred of such processing nozzles may be disposed in one of these units. If a non-advantageous flow profile of the melt is established in the area of the nozzles or due to fluctuating gas pressure for example, the melt is able to penetrate the nozzles. In the region of the nozzle orifices/nozzle openings, chemical reactions can lead to solids being deposited, for example deposits of magnetite (Fe 3 04) . This can lead to a successive "clogging" of the processing nozzles as the free nozzle cross-section becomes smaller. At a prevailing gas pressure, this can reduce the gas throughput per unit of time. Productivity decreases. It is not always possible to increase the gas pressure by using compressors. In this connection, a known approach is to clean the nozzles manually or mechanically with the aid of a ram device. The original cross-section for the gas circulation is restored again as a result. However, this can cause damage to the refractory lining around the nozzle openings and hence premature wear in this area. It is an object of the invention to propose a vessel for smelting metal, accommodating and -3 processing a metal melt, in particular a non ferrous metal melt, in which the nozzle area incorporating the nozzles remains fully functional for longer periods. In this connection, it should also be possible to retrofit existing units. In achieving this objective, the invention is based on the following knowledge. Figure 2 illustrates a cross-section through a part of a wall of a Peirce-Smith converter (illustrated in Figure 1) in the nozzle area, and a nozzle 10 may be seen extending from the outside through a metal casing 12 and a refractory lining 14 into an area of the converter in which a metal melt 50 is disposed. Figures 1 and 2 illustrate the converter in a position referred to as the "operating position". Accordingly, the nozzle 10 extends essentially horizontally in this position and in a plane perpendicular to the likewise essentially horizontally oriented longitudinal axis L-L of the converter. The opening region 10m extends slightly beyond the refractory lining 14 (in the case of a new installation illustrated by way of example here). A plurality of such nozzles 10 are disposed on the longitudinal face of the converter spaced at a distance apart from one another along an imaginary straight line, as schematically indicated in Figure 1. Via the nozzles 10, which have an internal diameter of 5 cm for example, the processing gas (air in this embodiment) is introduced into the melt 50, where it leaves the nozzle -4 10 in the form of relatively large bubbles 52 and rises. The bubbles are released from the nozzle in the region of the top part of the opening of the nozzle. During the course of the treatment process, a flow of melt 50 forms, as indicated by the arrows in Figure 2. The non-advantageous profile of the flow of melt in the vicinity of the nozzle opening and the pressure of the melt acting on the nozzle opening lead to melt penetration into the nozzle and the formation of solid deposits 10a at the bottom region of the nozzle opening, as schematically indicated in Figure 2. Due to the relatively large gas bubbles, the interface between the gas and liquid phase is relatively small. Furthermore, the dwell time of the large gas bubbles in the melt is short. Both factors lead to a low level of efficiency of the air introduced. In practice, therefore, it is necessary to introduce considerable quantities of air through the nozzles into the melt, which means long processing times and hence higher costs. Although using air with a higher proportion of oxygen shortens processing times, it leads to extreme temperature peaks in the region of the nozzle openings, thereby significantly increasing wear of the refractory lining 14. This simultaneously increases the risk of infiltration into the refractory lining 14 and/or deposits 10a in the opening region 10m of the nozzles 10. These problems can be avoided by a design of the type illustrated in Figure 3. Whilst the shape, disposition and number of nozzles 10 may remain essentially unchanged, the metal melting unit proposed by the invention is equipped with additional gas flushing devices 20, which are disposed underneath the nozzles 10 in an operating/working position of the unit. The gas flushing devices 20 -5 are used to introduce a gas into the metal smelt 50 in such a way that it rises adjacent to the refractory lining and in such a way that it is subsequently flushed around one or more nozzle openings 10m. "Flushed around" means that the gas leaving the gas flushing devices 20 (for example an inert gas such as argon) is directed towards the nozzle opening(s) 10m and passes the nozzle openings 10m as close as possible in front or along said nozzles. It has been found that the occurrence of deposits in the nozzle in the area of the nozzle opening thus being prevented or significantly reduced. The continual flushing (purging) around the nozzle opening ensures that a homogeneous velocity profile is created in the vicinity of the nozzle opening. The melt flow is advantageously affected in such a way that the melt does not get into the nozzle opening at all or does so to only a slight degree, and is no longer there to form deposits. Furthermore, the relatively small gas bubbles 54 introduced via the gas flushing device 20 lead to a melt-gas mixture, the density of which is lower than that of the pure melt. Consequently, the process gas (air or air-oxygen mixture) is able to penetrate the melt more deeply at the same intake pressure, which leads to a better dispersion (distribution) of the process gas. The time the air bubbles remain in the melt is also increased as a result so that, overall, a significantly improved reaction behaviour is established between the air bubbles 52 and the melt, thereby resulting in a more efficient use of the process gas. In its most general embodiment, the invention relates to a metallurgical melting and processing unit with the following features: -6 - a cylindrical shape with a longitudinal axis which extends essentially horizontally when the unit is in an operating position, - an outer metal casing, - an inner refractory lining, - several nozzles running from outside through the metal casing and refractory lining for introducing a processing gas into the metal melt via corresponding nozzle openings, - the nozzles are disposed mutually adjacent and at a distance to each other along the longitudinal face of the unit (in the direction of the longitudinal axis of the unit), - in the operating position of the unit, one or more gas flushing devices are disposed underneath the nozzles, through which a gas can be introduced into the metal melt so that it rises adjacent to the refractory lining and flows along one or more nozzle openings. The arrangement and design of the nozzles as well as of the gas flushing devices may be realized in different ways. As mentioned above, the nozzle openings in known furnaces of the described type usually lie adjacent to one another along an imaginary straight line. In the case of such a nozzle layout, the invention proposes that a co-operating (corresponding) gas flushing device be disposed underneath every nozzle. In other words, every nozzle is assigned a separate gas flushing device so that fine gas bubbles can be selectively directed from a gas flushing device towards the opening region of a co-operating nozzle.

Alternatively, a gas flushing device may also co-operate with a group of nozzles. This is specifically an option if the gas flushing device selected is one which has an end face at the gas outlet end which extends across a larger surface area, for example has a length spanning two or three adjacently disposed nozzles. Figure 4 illustrates such an embodiment (a view from the interior towards the refractory lining 14) of a converter of the type illustrated in Figure 1, but based on the design proposed by the invention with gas flushing devices 20 underneath the nozzles 10. As may be seen, ten nozzles 10 are disposed in a horizontal row and there is a space respectively between adjacent nozzles 10. Disposed underneath the nozzle row by approximately a nozzle diameter are seven gas flushing devices 20, and each gas flushing device 20 has a rectangular end face 20m at the gas outlet end. The size of the gas flushing devices 20 is such that the gas discharged from a gas flushing device 20, for example nitrogen, can be selectively directed to two nozzles 10 disposed above. Of course, the gas flushing devices 20 may have a different geometry, especially in the region of the end face at the gas outlet end and may have a circular end face, for example. However, also in this embodiment, one gas flushing device 20 may be provided for one nozzle 10 or alternatively also one (bigger) gas flushing unit for -8 several nozzles 10, for example. The layout of the gas flushing devices 20 is the same as the nozzle row in Figure 1 so that the gas outlet surfaces of the gas flushing devices 20 are mounted along an imaginary straight line lying parallel with the axis of the converter. It is likewise possible for the gas flushing devices 20 to be positioned offset from one another at different heights in the refractory lining 14. As illustrated in Figure 3, the gas flushing devices 20 are installed such that they extend through the metal casing 12 and refractory lining 14 in the same way as the nozzles 10. As explained above, the purpose and function of the gas flushing devices 20 is to direct the finest possible gas bubbles in front of the opening region of the nozzles 10 in order to influence the melt flow there in order to prevent melt entering the nozzle and deposits being formed in the nozzle and to make better use of the process gas. In this respect, the nozzles and gas flushing devices are significantly different from one another in terms of construction and function. The nozzle has a large free internal cross-section (e.g. > 500 mm 2 ) through which the gas flows. In the case of a gas flushing device, the gas is conveyed along homogeneously extending individual passages, each with a significantly smaller internal cross-section (in particular < 50 mm 2 ) or through a pore structure. Porosity may be said to be directed or non-directed.

-9 Non-directed porosity is similar to a sponge-type structure where the gas seeks an irregular path through the ceramic base material of the gas flushing brick depending on the pore structure. Such gas flushing devices with non-directed porosity are known and will therefore not be described in further detail here. In the case of gas flushing devices 20 with directed porosity, the gas is directed through the flushing element via discrete gas passages with a selective flow direction. It would also be possible to opt for a combination of directed and non-directed porosity inside a gas flushing device 20 or within a row of gas flushing devices 20. In this case, the penetration depth of the process gas in the smelt 50 can also be selectively adjusted. The process gas is the gas fed through the nozzles 10. The arrangement proposed by the invention results in a reduction in temperature peaks and a largely homogenous temperature profile of the melt in the area around the nozzle opening. Refractory wear is significantly reduced. Penetration of the nozzle opening by melt and deposits in the nozzle opening are significantly reduced. The overall nozzle cross-section remains free for a longer period, requiring no cleaning, and the process gas is introduced much more constantly than is the case with the prior art. Down-time of the unit is minimised. In parallel, costs can be reduced. This also applies when - 10 additional gas flushing devices 20 are provided because they have a considerable service life and the service life of the nozzles 10 is also made significantly longer compared with the prior art. When the unit is in the working position with the nozzles disposed horizontally as described above, it is possible for the gas flushing devices 20 to be disposed so that the projections of the longitudinal axis of the nozzles 10 and gas flushing devices 20 form an acute angle between them on a plane perpendicular to the longitudinal axis L-L of the unit, as illustrated in Figure 3, where the corresponding angle is denoted by a and is approximately 300. The nozzles 10, like the gas flushing devices 20, are usually disposed at the bottom part of the unit when it is in its operating position, as may be seen from the presentation of Figures 1 to 3. The gas flushing device 20 illustrated in Figures 3 and 4 is a gas flushing brick which has a non-directed porosity end to end, and the gas (in this instance nitrogen) is directed via a gas intake line 22 and a gas distributor chamber 26 disposed between the gas intake line 22 and the porous refractory part 24. Such a gas flushing brick has been part of the prior art for centuries but was used for other applications. In the illustration of Figure 3, the end face 20m of the gas flushing device 20 at the gas outlet end lies flush with the internal face of the refractory lining 14 but may also project slightly beyond it into the metal melt - 11 50. In any case, the end face 20m at the gas outlet end is in direct contact with the melt 50 during the flushing operation. When talking of large or small gas bubbles within the context of the invention, this should specifically be taken as meaning the following in quantitative terms. The gas bubbles introduced into the metal melt 50 via the gas flushing devices 20 typically have a bubble diameter of < 10 mm. Gas flushing devices 20 with directed porosity have gas passages for this purpose, the free internal cross-section of which for the gas transport is < 15 mm 2 , < 25 mm 2 or < 50 mm 2 respectively. Gas flushing devices 20 with non-directed porosity made from porous refractory material may be designed so that the gas permeability has the following values conforming to EN 993-4 (1995): > 2 x 10~12 M 2 , > 15 x 10~12 M 2 , > 50 x 10-12 Mi 2 , < 200 x 10~12 M 2 . The ratio between the mean diameter of the bubbles fed through the nozzles 10 and the mean diameter of the bubbles fed through the gas flushing device 20 is usually 10 : 1 to 200 : 1. The quantities of gas introduced into the smelt via the gas flushing devices 20 and the nozzles 10 are based on similar relationships. For example, a gas quantity of 0.02 to 0.5 Nm 3 /min is introduced through every gas flushing element, 10 and 20 Nm 3 /min through every nozzle 10.

12 In the case of a newly installed unit (as illustrated in Figure 3), the shortest distance between the nozzles 10 and co-operating gas flushing devices 20 on the side of the refractory lining facing the melt may be 2 to 100 cm, for example 5 to 50 cm. The angle o: between the projection of the nozzle axis and the projection of the axis of the co-operating gas flushing device on a plane lying perpendicular to the longitudinal axis L-L of the unit may be 10* - 80', preferably 10 40". With reference to the use of the word(s) "comprise" or "comprises" or "comprising" in the foregoing description and/or in the following claims, unless the context requires otherwise, those words are used on the basis and clear understanding that they are to be interpreted inclusively, rather than exclusively, and that each of those words is to be so interpreted in construing the foregoing description and/or the following claims. A reference herein to a patent document or other matter which is given as prior art is not taken as an admission that that document or prior art was part of common general knowledge at the priority date of any of the claims.

Claims

1. Metallurgic melting and treatment vessel comprising the following features: 1.1 a cylindrical shape with a longitudinal axis (L-L) extending essentially horizontally in an operating position, 1.2 an outer metal shell (12), 1.3 an inner refractory lining (14), 1.4 various nozzles (10) extending from the outside through the metal shell (12) and the refractory lining (14) for introducing a treatment gas into the metal melt (50) via corresponding nozzle mouths (10m), 1.5 the nozzles (10) are arranged at a distance to each other at the long-side of the vessel, 1.6 in the operating position of the vessel one or several gas-flushing installations (20) are arranged below the nozzles (10) through which a gas can be introduced into the metal melt in such a way that it will ascend adjacent to the refractory lining thereby blowing against one or several of the nozzle mouths (lOim), 1.7 the gas-flushing installation (20) have a directed or random porosity so that gas bubbles, that are introduced by the gas-flushing installation (20) into the metal melt, have a bubble-diameter < 10 mm.

2. Vessel according to claim 1 wherein the nozzle mouths (10m) are arranged along an imaginary line next to each other.

3. Vessel according to claim 1, wherein a corresponding gas-flushing installation (20) is arranged below each nozzle (10).

4. Vessel according to claim 1, wherein one gas flushing installation (20) is arranged below a group of nozzles (10). - 14

5. Vessel according to claim 1, wherein at least one gas-flushing installation (20) provides at least at its gas outlet end a random porosity.

6. Vessel according to claim I wherein at least one gas flushing installation (20) has at least at its front face (20m) of the gas outlet end a rectangular cross-section.

7. Vessel according to claim 1, wherein the gas-flushing installations (20) are arranged along an imaginary line next to each other.

8. Vessel according to claim 1, wherein the gas-flushing installations (20) extend from the outside through the metal shell (12) and the refractory lining (14) and their front face (20m) at the gas outlet end is in contact with the molten metal in an operating position,

9. Vessel according to claim 1, wherein the nozzles (10) and the gas flushing installations (20) are arranged to each other in such a way that between their corresponding longitudinal axis a sharp angle a results.

10. Vessel according to claim 1, wherein the nozzles (10) in their operating position are extending essentially horizontally.

11. Vessel according to claim 1, wherein the nozzles (10) in their operating position extend along the lower part of the receiving- and treatment vessel. BA .6923i3