EP3139120B1

EP3139120B1 - Delta roof with improved cooling for electric smelting furnaces

Info

Publication number: EP3139120B1
Application number: EP16185997.0A
Authority: EP
Inventors: Gian Luca Masnata
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-08-27
Filing date: 2016-08-26
Publication date: 2018-08-01
Anticipated expiration: 2036-08-26
Also published as: ES2693147T3; ITUB20153270A1; EP3139120A1; TR201815809T4

Description

The present invention relates to an improved delta roof for electric smelting furnaces.
In particular, the present invention relates to a delta roof provided with an improved integrated cooling system for cooling the electrodes that conduct the melting process.
In general terms, the present invention is mainly applicable in the iron and steel production field, in connection with the melting of iron scrap in electric smelting furnaces in which the roofs (delta) are utilised in such furnaces as closure elements.
In order to allow the contact of the electrodes with the material to be melted arranged in the furnace, the delta roofs are provided with through-holes, usually three in number, which act as channels for introducing the electrodes.
As known, for reasons of transportability and movement of the delta roofs, these can be made as a single block of refractory material in the case of delta roofs of small dimensions, or as a plurality of independent but mutually complementary sectors, which will then be assembled at the mounting time in the steelworks.
In the economics of hot-working in steelworks with electric smelting furnaces, a significant issue is the consumption of kg of electrode for each tonne of steel produced.
In order to reduce this consumption, a known solution is to equip the delta roof with particular means for cooling the electrode.
An example of these means for cooling the electrode is disclosed in US4852120 patent, where support clamps for supporting the electrode equipped with a series of nozzles for dispensing nebulized water are provided in the outer zone of the delta roof.
Still according to US4852120 , other nozzles can also be provided directly on the delta roof at the inlet of the electrode. Also EP-A 0029416 relates to a cooling panel for the roof of an electric furnace comprising channels for cooling fluid converging toward the electrode sleeve. Although these embodiments actually provide lengthening the working life of the electrode, nevertheless they have some drawbacks.
In fact, due to the dusty and aggressive environments where the nozzles operate, the latter tend to become rapidly obstructed, therefore much reducing the efficiency of the cooling system.
Furthermore, the movement of the electrodes from the working zone to the rest zone inevitably transports a significant quantity of waste, such as sprays of steel, dust etc., which tends to obstruct the nozzles.
In this case, it is therefore necessary to clean the nozzles or to replace them.
However, disadvantageously, in order to carry out these tasks, i.e. the cleaning, removal and replacement of a cooling nozzle, it is necessary to interrupt the production cycle, since the nozzles are close to the electrode introduction channel.
The aim of the present invention is to make an improved delta roof for electric smelting furnaces that is able to overcome the above-mentioned drawbacks of the prior art in a very simple, economical and particularly functional way.
A further aim is to make an improved delta roof for electric smelting furnaces in which the periodical cleaning of the nozzles for cooling the electrodes, or the replacement thereof, does not require removing the delta roof, interrupting the production cycle and in general working under dangerous conditions.
These aims according to the present invention are attained by making a delta roof for electric smelting furnaces wherein channels are obtained directly in the refractory material, said channels converging from the outside in correspondence with the passages of the electrodes, wherein lances are housed in such channels in a sliding manner, said lances being provided with nozzles for cooling the electrodes.
In particular, these channels converge towards the passages of the electrodes substantially horizontally or with an inclination of less than 20° with respect to the horizontal.
On the contrary, the prior art, for example US4852120 , provides a cooling system located vertically and parallel with respect to the electrode.
In this way, in order to clean or remove a nozzle it will be sufficient to exert an extraction action on the relative lance in a safe position far away from the electrode.
In this way, advantageously, in addition to the increase in safety, no shutdown of the plant will be required since several mutually independent lances will be directed on the same nozzle.
Further characteristics of the invention are highlighted in the dependent claims.
The characteristics and advantages of a delta roof for electric smelting furnaces according to the present invention will become clearer in the following description, made by way of non-limiting example, with reference to the accompanying schematic drawings in which:

figure 1 is a schematic view from above of a delta roof for electric smelting furnaces according to the present invention;
figure 2 is a schematic section view of the delta roof of figure 1;
figure 3 is a schematic lateral view of the delta roof of figure 1.

With reference to the figures, an embodiment of a delta roof for electric smelting furnaces according to the present invention is shown.
Such a delta roof is at least partially made of refractory material and comprises at least one through-opening 15 for introducing from the outside an electrode for conducting the melting process.
According to the invention, the delta roof comprises a plurality of channels 18 obtained directly in the refractory material in such a way that from the outside of the delta roof they converge at the through-openings 15.
In particular, said channels 18 converge towards the passages 15 of the electrodes substantially horizontally or with an inclination of less than 20° with respect to the horizontal so as to be able to utilise the whole thickness of the refractory coating.
A lance 17 is arranged inside each channel 18 in a sliding manner, said lance 17 being independently supplied with a cooling fluid and being provided with nozzles 16.
These nozzles 16 are arranged on the relative lance so as to face the electrodes for conducting the melting process when the lance is inserted in the channel 18. In case of cleaning or of need to remove a nozzle, it is sufficient to extract the relative lance from the delta roof, acting safely far away from the through-opening 15.
In order to allow the correct positioning of the lance in the relative channel, end-strokes and angular orientation elements configured for guaranteeing the correct positioning of the nozzles with respect to the electrodes to be cooled are provided.
For each through-opening 15, at least two, preferably four, channels 18 are provided, so that, even removing a lance, at least another lance is in action with its nozzles on the relative electrode.
Depending on the consumption of the refractory material and of the thickness of the wall through which the electrode passes, the lances will be positioned more or less retracted with respect to the passage itself in order to prevent the rapid deterioration thereof.
Advantageously the accesses to the channels 18 are arranged laterally with respect to the delta roof and the inner walls of the openings are provided with holes 19 for the passage of cooling fluid from the nozzles to the electrodes.
Furthermore, the present invention allows preserving the refractory material for a longer time, increasing the number of casts per delta roof.
In fact, in order to melt the scrap to be brought to the liquid state, the temperature reaches about 1700-1800° Celsius, subjecting the refractory material to the melting limit thereof.
Thanks to the lances introduced in the channels obtained in the very refractory material, the above-described system also contributes cooling the refractory material itself.
Thus, it can be observed that a delta roof for electric smelting furnaces according to the present invention attains the aims previously set forth.
In fact, the delta roof for electric smelting furnaces of the present invention on the one hand comprises cooling nozzles for cooling the electrodes and on the other hand does not require breaks in the production cycle for cleaning or removing them.
The delta roof for electric smelting furnaces of the present invention as it is conceived is susceptible to numerous modifications and variants, all falling within the same inventive concept; moreover, all the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the dimensions thereof, can be of any type according to the technical needs.

Claims

Delta roof (10) for electric smelting furnaces of the type at least partially made of refractory material and comprising at least one through-opening (15) for introducing an electrode for conducting the melting process from the outside into said furnace; characterized in that said delta roof (10) comprises a plurality of channels (18) obtained in said refractory material, which converge from the outside of said delta roof at said at least one through-opening (15), a lance (17) being arranged in a sliding manner inside each of said channels (18), said lance (17) being independently supplied with a cooling fluid and being provided with nozzles (16), said nozzles being arranged on said lance so as to face said electrodes for conducting the melting process when said lance is inserted in said channel (18).
Delta roof according to claim 1 characterized in that said channels (18) comprise end-strokes configured to ensure the correct positioning of the nozzles with respect to said electrodes.
Delta roof according to any preceding claims characterized in that for each through-opening (15) at least two channels (18) are provided, preferably four.
Delta roof according to any preceding claims characterized in that the accesses of said channels (18) are arranged laterally to said delta roof and have a substantially horizontal development.
Delta roof according to claim 4 characterized in that said channels (18) have a substantially horizontal development comprised within ± 20° with respect to the horizontal.
Delta roof according to any preceding claims characterized in that the inner walls of said through-openings are provided with holes (19) for the passage of the cooling fluid from said nozzles to the electrodes.