Industrial electric heating furnaces – Arc furnace device – Plural furnace units
Reexamination Certificate
1999-11-23
2001-03-13
Hoang, Tu Ba (Department: 3742)
Industrial electric heating furnaces
Arc furnace device
Plural furnace units
C373S079000
Reexamination Certificate
active
06201826
ABSTRACT:
FIELD OF APPLICATION
The invention is applied in the field of steel production to load electric furnaces with scrap, or base material similar to scrap, which is pre-heated by means of the fumes leaving the electric furnaces themselves and flowing from the top downwards.
The electric arc furnaces to which the invention is applied can be of the type fed by either direct or alternating current.
The invention can be employed both on new installations appropriately prepared, and also for revamping of existing installations using furnaces of a conventional type.
The invention makes it possible to reduce the times required to open the roof of the furnace in order to load it, limiting heat losses from inside the furnace towards the outer environment.
Moreover, the invention makes it possible to automate the movements needed to load the furnace, to drastically reduce the times of the cycle by reducing the stoppages of the furnace, to limit the movements and equipment necessary for loading, to reduce the spaces occupied at the sides of the furnace, and also to use loading baskets of either small or large capacity according to availability.
A further advantage of the invention is that, in order to pre-heat the scrap and unload it into the furnace, it is possible to use directly the baskets arriving from the scrap accumulation store or baskets which are loaded when they are already positioned in the pre-heating station; the baskets may be of variable shape, size and type, and do not require stationary supporting structures when they are in the pre-heating position near the furnace.
STATE OF THE ART
The state of the art includes electric arc furnaces used to produce steel from scrap and regenerated material of various types.
In the state of the art, the furnaces can be loaded continuously, for example by means of conveying means such as a belt, connected with the inside of the furnace and fed continuously with fresh scrap which gradually replaces that already loaded into the furnace.
In another solution, the furnaces are loaded moving means, for example bridge cranes, in correspondence with the mouth of the furnace which is kept temporally open.
The bottom of the basket is then opened and the material is unloaded inside the furnace. For this purpose the baskets are equipped at the bottom with movable doors, valves, teeth, sliding grates or other appropriate opening system.
Systems using baskets for loading the furnace which are known to the state of the art have a plurality of disadvantages.
Firstly, it takes a long time to load the furnace due to the combination of movements required to open the furnace and position the basket; this causes a considerable heat loss from inside the furnace towards the outside, and also the leakage into the surrounding environment of fumes containing powders, particles and other pollutants.
A further disadvantage is that if the scrap is loaded cold into the furnace, it takes longer to melt and causes problems for the penetration of the electrodes.
At present, in some steel plants the furnaces are loaded with scrap which is pre-heated by the heat of the fumes discharged from the furnace itself through the fourth hole on the roof.
Loading systems known to the state of the art where the scrap is pre-heated use loading baskets located in the appropriate rooms into which the fumes are conveyed before they are purified and discharged by the appropriate plants.
There are also solutions known to the state of the art which include a single room which contains several loading baskets, or several rooms connected to each other, each one of which contains a single loading basket.
These systems cause problems in the structuring of the rooms, the movements of the baskets and wear on the baskets too.
Moreover, in the case of baskets heated inside the room, the scrap loses part of the heat it has accumulated, both when it is removed from the room and when it is transported to near the mouth of the furnace and also when it is unloaded into the furnace, from which there is always and in any case a considerable heat loss. The scrap moreover is not heated uniformly from one basket to the next.
These systems furthermore are not very functional, they are very expensive, and they take up a great deal of space inside the plant.
A further disadvantage is that the pre-heating rooms are normally located in positions which are not very near the furnace, and therefore the times needed to transport the baskets from this position to the furnace are very long and the heat losses are very high.
WO 96/32616 teaches to heat the scrap in a container which is solid with a movement structure, the scrap being heated from the bottom upwards.
This teaching does not give the advantages of heating the scrap from the top downwards, it does not allow the use of autonomous baskets, nor does it allow easy maintenance operations.
WO 92/10594 uses a manipulation tower comprising at least a rotary arm which is used to position a container full of scrap from a pre-heating position to a position wherein the scrap is loaded into the furnace, and vice versa.
WO'594 includes a pre-heating environment which is open at the top and at the bottom, inside of which a loading container, with a bottom which can be opened, is positioned.
The pre-heating environment is located on a stationary base which constitutes a pedestal arranged in proximity with the furnace; it is associated, in the pre-heating position, with air-tight closing means to close its ends, and means to introduce and discharge the pre-heating fumes taken from the furnace.
The pre-heating environment includes a mantle which flares towards the bottom and which is connected to the lower pedestal so as to constitute an air-tight seal.
The pedestal communicates with a lower chamber wherein the fumes pass and are combusted.
The hot fumes emerging from the furnace are first directed into the combustion chamber below the pre-heating container where they are burnt, and then conveyed through the appropriate ducts, either inside the container from the top downwards, during the pre-heating step, or they are directed towards the discharge plant, during the movement or filling of the container itself.
This solution involves expensive and complex fitting of the pipes, difficulties of installation, loss of temperature on the part of the fumes which, due to the long and tortuous path they have to follow, are cooler when they reach the scrap.
Moreover, this solution involves problems of pollution and wear of the filter systems because after the fumes have passed through the scrap, they are sent directly to the treatment and discharge plant, and therefore they carry with them all the powders, slag and particles which they have absorbed during their passage through the container.
Generally speaking, the solution given by WO'594 does not make it possible, or at least easy, to use loading baskets of any shape and size whatsoever, given that the baskets need to be inserted inside the pre-heating environment arranged resting on the stationary base.
EP-A-629830 provides a variant to WO'594 where the fumes are introduced into the container full of scrap from the top downwards, and where there is a pre-combustion of the fumes entering the container and also a post-combustion of the fumes as they emerge therefrom.
WO 95/12690 describes a movement system with a rotary tower for containers in which to pre-heat the scrap; the system does not use baskets of the removable type but a substantially stationary single-block structure, which involves obvious limitations to the versatility, flexibility and operativity of the plant.
Moreover, the means by which the pre-heating fumes are treated and discharged after they have passed through the container of scrap are not explained.
FR-A-2.435.684 includes a movement system with articulated arms associated with a movable structure which can be translated above a melting furnace.
This document does not include any pre-heating of the scrap or any processes to convey and discharge the fumes.
EP-A-287.550 provides a procedure to pre-h
Della Negra Angelico
Giannoulidis Ioannis
Losciale Matteo Vittorio
Antonelli Terry Stout & Kraus LLP
Danieli & C. Officine Meccaniche SpA
Hoang Tu Ba
LandOfFree
Loading system for electric arc furnaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Loading system for electric arc furnaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Loading system for electric arc furnaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2453222