WO1997021965A1

WO1997021965A1 - Lining of furnace

Info

Publication number: WO1997021965A1
Application number: PCT/SE1996/000093
Authority: WO
Inventors: Staffan GRANSTRÖM
Original assignee: Essge Systemteknik AB
Current assignee: Essge Systemteknik AB
Priority date: 1995-12-12
Filing date: 1996-01-30
Publication date: 1997-06-19
Anticipated expiration: 1998-06-12
Also published as: AU4959796A; SE9504444D0

Abstract

This invention relates to a panel for furnaces, which are intended to be used when smelting steel by means of so-called high-temperature processes, the panel being intended to be an integral part of wall constructions and/or ceiling constructions of the furnace, and the panel in application position having an outside and an inside. According to the invention the panel is characteristized by the combination of the following features: the outside of the panel (2) has an elongated cooling means (7), which is arranged in that way that a cooling medium can stream through the same, and that pipe means (8, 9) are arranged for conducting the cooling medium into and out from, respectively, the cooling means (7), the cooling means having an extension in the cross-direction, which corresponds to the distance (A); the inside of the panel (2) is covered by a thick layer of fireproof material (10), the thickness (B) of which is as great as or greater than the distance (A); the panel (2) has a great number of bar-like or plate-like means (11) which are arranged at different levels over the entire cooling means (9), the bar-like or plate-like means (11) essentially penetrating the layer of fireproof material (10).

Description

LINING OF FURNACE

This invention relates to a panel for furnaces, which are intended to be used when smelting steel by means of so called hightemperature processes, the panel being intended to be an integral part of wall- and/or ceiling constructions of the furnace, and the panel in application position having an outside and an inside. Hightemperature processes have been developed concurrently with the development with ceramic walls and ceilings. A limited durability and the costs in connection herewith have enforced a development towards cooled, autogene wall- and ceiling panels.

The first step was watercooled box panels with better and not so well controlled water flow and a limited pressure and a limited temperature, which led to frequent crack formations in the panels with a great maintenance as a result.

Next step of the development came at first hand within the energy side (a low surface load) with watercooled tube panel walls with or without intermediate tube fin. Due to that fact a controlled water flow was received in all wall parts and a considerably less tensions, built- in, as a result and by that much more durable constructions. Tube panels were also quickly accepted after countless safety analyses within hightemperature processes as in soda furnaces, fuming furnaces and metallurgic furnaces, and as in wall panels and arch panels in electric arc furnaces. However, a higher temperature level in the furnace space quickly increases the surface load by radiation and by that tension levels in the material and the weld joints with a shortened lifelength and strongly increased energy losses to cooling water as a result.

These increased energy losses must be compensated either with an increased energy addition or an increased amount of fuel, which gives increased outlets of carbon dioxide, nitric oxides and hydrocarbons during combustion.

In later times also a spraycooled wall and arch panel has been developed for in first hand electric arc furnaces with a less need of cooling water quantities in the system, but for the rest with on the whole the same limitations and losses as for tube panels.

During later times large amounts of money have been spended in the world on further developments of smelt reduction processes and other rapid high temperature processes.

These process ideas, however, have not been spread so much, since the consequence thereof would be a high consumption of fireproof material and/or too high cooling losses and too high energy consumption due to defective wall and ceiling constructions, which without exception are weak points. In order to reduce the maintenance in existing plants, increase the share of cooled wall and ceiling surfaces, make possible a rapid development within metallurgic processes, hightemperature destruction processes and energy processes is accordingly required a new building element with the quality to be cooled, to resist a very high process temperature, to have low tension levels, low cooling losses per area unit and a minimum of expensive fireproof material.

By the allowed, published Swedish patent application 436.380 is previously known a cooling block for a furnace vessel, which block comprises a coil of cooling tubes, lying free towards the middle of the vessel. This coil of cooling tubes, which has no protecting fireproof material on its inside, is to a high extent exposed to the high temperatures existing inside of the vessel and can accordingly be damaged with great costs as a result.

These problems with known technique have been eliminated by the device according to the invention which relates to a energy-saving duplex panel for high surface temperatures. With duplex panel is meant a panel comprising several different materials in the purpose of reducing the heat losses through the panel and increasing the durability of the panel.

The panel according to the invention shall be described more closely below with reference to the accompanying drawings, in which Fig. 1 shows a plan view of a furnace which is provided with the panel according to the invention, Fig. 2 shows a section along the line II-II of Fig. 1 , Fig. 3 shows a separate panel according to the invention, seen as it would appear from the inner part of the furnace, and Fig 4 shows a view of the panel according to Fig. 3, seen in the direction of the arrows IV-IV.

Referring to Figs. 1 , 2 is shown there a furnace 1 , which has an essentially conventional design, but which distinguishes from the conventional furnaces by being provided with the panel 2 according to the invention. The furnace intended for smelting steel has in similarity with conventional furnaces a lower portion 3 of fireproof material. Furthermore, the furnace has an upper portion 4, in which the panels according the invention are arranged.

As is apparent from Figs. 1 , 2 the furnace has essentially circular form. In this connection the wall of the upper portion 4 comprises the panels 2a, b, c, d, according to the invention, which are put together to a unit.

In Fig. 1 are shown only four panels 2a-d, but of course the number of panels is more than four, because the panels are intended to extend around the entire circumference. In Figs. 3, 4 is the panel according to the invention shown loosened from the furnace. Each panel 2a-d has the design of a wall portion of a circular cylinder and accordingly has a vertical extension, which also appears from Fig. 2.

The outside 5 of the panel has a plurality of vertical pipe means 6a-h comprising pipes, which are coupled in series for forming an effective cooling means 7 and through which a cooling medium, for instance water, is intended to stream. In this connection a horizontal pipe means 8 intended to conduct water into the cooling means, whereas another horizontal pipe means 9 is intended to conduct water out from the cooling means. This means 7 has an extension, seen in the radial direction of the furnace, which corresponds to the distance A.

The inside of the panel according to the invention is covered by a thick, homogenous layer of a suitable fireproof material 10, the thickness of which (see the distance B in Fig.

4) is as great as or greater than the radial extension of the cooling means 7. With homogenous is meant that the layer of fireproof material 10 covers the entire inside of the panel.

By application of the thick, fireproof material 10, the new panel gets an extremely good resistance against high temperatures. An essential problem, however, could arise in connection herewith, and that would be a high consumption of fireproof material, which would be very costly not only regarding the material itself but also regarding the work itself to exchange the damaged material.

According to the invention this mentioned problem has been solved by the fact that a great number of horizontal, bar-like means 11 are arranged at different levels in each vertical pipe 6a-h, and these horizontal means 11 extend through the layer of fireproof material 10 and has essentially the same length as the radial extension of the material 10. The bar-like means 11 with their inner end portions are intended to be in close contact with the vertical pipe means 6a-h. Due to that fact the means 11 , which are arranged in the thick, fireproof material 10, and which preferably are made of copper, will suck up heat from the material 10 and take the heat further to the pipe means 6a-h for conducting away the heat. This means that the fireproof material is spared from being destroyed by burning, which accordingly makes possible to use the effective hightemperature processes when smelting the steel.

The bar-like means 11 can either be solid or tubular with different types of cross sections. Furthermore, the means could be plate-formed. The important thing is that the means 11 effectively suck up and conduct the heat away from the fireproof material. In order that this shall be completely successful, there is required a good cooperation between the means 11 and the effective cooling means 7. Thus, according to a preferred embodiment the bar-like or the plate-like means 11 are fastened to the pipes 6a-h of the cooling means. Besides the fact that there will be a good heat conduction from the means 11 to the cooling means 7, the fastening of the means 11 to the pipes 6a-h has the consequence that the means 11 contribute to hold the fireproof material to the pipes.

The invention is of course not limited to the shown and mentioned embodiment but can be modified within the scope of the following claims. Thus, the new invention idea could of course be applied partly in wall panels for other types of furnaces, partly in ceiling panels for different types of furnaces. Furthermore, the outside of the panel can have another design than the one shown with pipes. Thus, the pipe could be exchanged for a cooling means which has a plate-like design and comprises an inner wall and an outer wall, between which the cooling medium can stream.

Claims

1. A panel for furnaces, which are intended to be used when smelting steel by means of so called hightemperature processes, the panel being intended to be an integral part of wall constructions and/or ceiling constructions of the furnace, and the panel in application position having an outside and an inside, c ha r ac te r iz e d by the combination of the following features:

- The outside of the panel (2) has an elongated cooling means (7), which is arranged in that way that a cooling medium can stream through the same, and that pipe means (8, 9) are arranged for conducting the cooling medium into and out from, respectively, the cooling means (7), the cooling means having an extension in the cross-direction, which corresponds to the distance (A);

- The inside of the panel (2) is covered by a thick layer of fireproof material (10), the thickness (B) of which is as great as or greater than the distance (A);

- The panel (2) has a great number of bar-like or plate-like means (11) which are arranged at different levels over the entire cooling means (9), the bar-like or plate-like means

(11) essentially penetrating the layer of fireproof material (10).

2. A panel according to claim 1, the cooling means (7) comprising a plurality of parallel pipes (6a-h), which are coupled in series, characterized in that the bar¬ like or plate-like means (11) are made of copper.

3. A panel according to claim lor2, characterized in that the bar-like or plate-like means (11) are fastened on the cooling means (7), so that they contribute to hold the fireproof material (10) on the cooling means (7).