GB2155160A

GB2155160A - Charging apparatus for a melting furnace

Info

Publication number: GB2155160A
Application number: GB08503856A
Authority: GB
Inventors: Luciano Fabris
Original assignee: Gautschi Electro-Fours SA; GAUTSCHI ELECTRO FOURS AG
Current assignee: Gautschi Electro-Fours SA; GAUTSCHI ELECTRO FOURS AG
Priority date: 1984-02-21
Filing date: 1985-02-14
Publication date: 1985-09-18
Also published as: JPS60253785A; FR2559887A1; CH661788A5; DE3444181A1; GB8503856D0

Abstract

Charging apparatus (3) is arranged immediately before a melting furnace (2) for metal, e.g. Al, scrap and comprises a preheat chamber (5) in which a charging bin (6) is arranged which is mounted on a carriage (11) for transport via doors (16, 17) into the melting chamber (15) of the furnace (2). The scrap metal introduced into the bin (6) through a supply chute (9) is uniformly distributed by a vibrator device (10) and is subjected to a rapid preheating by the hot exhaust gases of the furnace (2) admitted via nozzles (21) to the chamber (5). Hot gases from the preheat chamber (5) and, if desired, fresh air can be mixed with these exhaust gases to regulate the preheating temperature. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a charging apparatus for a melting furnace The present invention relates to metal melting furnaces and, more specifically, pertains to a new and improved construction of a charging apparatus for a melting or foundry furnace for melting-down non-ferrous metal scrap, especially aluminium scrap, and having a charging bin.

It is known to the artto preheat charges of aluminium scrap in preheater installations which are heated by the exhaust gases of melting or foundry furnaces. Combustible contaminants and impurities adhering to the scrap are thereby removed by roasting or carbonizing. The preheated scrap is subsequently transported in charging bins, for instance by means of a crane, to the melting or foundry furnace and is there introduced into such melting or foundry chamber by tipping the charging bin or by inserting the charging bin by means of a hydraulic ram.

It is also known to introduce scrap by means of so-called vibrator troughs which distribute the mate rial to be melted over the hearth surface. Since the roasting or carbonizing of the contaminants or impurities, respectiveley the preheating, occurs in chambers remote from the melting or foundry furnace, the often relatively long transport distances have a detrimental effect due to the required trans port time and the thereby arising temperatures losses.

Therefore, it is a primary object of the present invention to provide a new and improved construc tion of a charging apparatus of the previously mentioned type which does not exhibit the aforementioned drawbacks and shortcomings of the prior constructions and which permits savings of energy in scrap metal melting by an improved exploitation of the heat of the furnace exhaust gases, and in particular in which the heat transfer from the hot gases to the scrap metal is improved and which, further, is relatively simple in construction and design, extremeiy economical to manufacture, high ly reliable in operation, not readily subject to break down or malfunction and requires a minimum of maintenance and servicing.

To this end, the charging apparatus of the present invention is manifested by the features that it comprises an integrated preheat chamber in which the charging bin is arranged. The charging bin serves as a receiving or accumulating bin for accommodating the scrap metal introduced through a chute. Nozzles are provided in the preheat cham ber which blow high-velocity hot gas emanating from an exhaust conduit of the melting or foundry furnace and from a mixing system directly onto the scrap metal. The charging bin is transportable into the melting or foundry chamber of the melting or foundry furnace. The melting or foundry furnace is arranged immediately subsequent to the charging apparatus.

Both substantial time savings and reduced tem perature losses result from the fact that the charging bin is arranged in the preheat chamber of the charging apparatus and is filled with scrap metal directly from above through a gravity or drop chute and, after being preheated, is transportable into the melting furnace arranged immediately subsequent to the charging apparatus. Due to the direct blowing of high-velocity hot gas onto the scrap metal in the charging bin, energy is saved in this rapid preheating. The transfer of heat is improved which also reduces the duration of the preheat interval.

The transportability of the charging bin is preferably effected by a powered or driven carriage which is advantageously arranged externally to the preheat chamber which is thermally insulated. This avoids detrimental temperature effects.

A vibrator apparatus or device, which may be an eccentric-type vibrator device, mounted on the carriage is of particular advantage. The vibratory motion transmitted through the charging bin achieves a good distribution of the scrap metal overthecharg- ing bin which substantially improves the heat transferfrom the impinging hot gases to the scrap metal, since the heat absorbing surface of the scrap metal impinged upon by the hot gases is increased as a whole. Since the vibratory motion also produces a uniformly thick layer of the scrap metal introduced into the charging bin, the scrap metal is more rapidly and completely heated.The vibratory motion as well as a simultaneous reverse motion of the charging bin improve the distribution of the scrap metal upon the hearth of the melting or foundry furnace, respectively in the melt or molten pool of metal situated therein. Due to the shorter melting-down time, both the fire waste or burn-up loss and the energy requirements are reduced.

In a particularly advantageous embodiment of the invention, the exhaust gas conduit of the melting or foundry furnace, the hot gas removal or exhaust conduit of the preheat chamber as well as, if desired, a fresh air supply conduit all open into the mixing system in which these gases are mixed to achieve a predetermined hot gas temperature. In order not to melt the scrap metal in the preheat chamber, the temperature of the mixed hot gas which is conveyed through a subsequent hot gas recirculating blower into the preheat chamber, must be regulated beneath the melting point of the scrap metal. The melting point of aluminium and its alloys lies in the range of approximately 600 to 620 Celsius.To ensure that an excessively high temperature of the hot gas does not arise, a supplementary fresh air supply conduit with a regulated damper valve is provided leading to the mixing system.

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein throughout the various figures of the drawings there have been generally used the same reference characters to denote the same or analogous components and wherein: Figure 1 schematically shows the charging apparatus, partially in section, with the associated melting or foundry furnace; and Figure 2 schematically shows the recirculation system of the gases.

Describing now the drawings, it is to be understood that to simplify the showing thereof only enough of the structure of the charging apparatus has been illustrated therein as is needed to enable one skilied in the art to readily understand the underlying principles and concepts of this invention.

Turning now specifically to Figure 1 of the drawings, the charging apparatus 3 illustrated therein by way of example and not limitation and arranged on the foundry room floor, will be seen to be arranged immediately before a melting orfoundryfurnace 2, which may be of, for instance, the tub or vat furnace type, for melting-down clean aluminium scrap, e.g.

rolling mill scrap. The charging apparatus comprises integrated preheat chamber 5 in which a charging bin 6 transportable on rollers 7 is situated. Scrap metal 8 from a not particularly shown elevating conveyor bucket or equivalent structure is introduced through a gravity or drop chute 9 from above into the charging bin 6 designed to serve as a receiving or accumulating bin.

After the charging bin 6 has been loaded, an operation requiring about two or three minutes, the charging bin 6 is vibrated by means of a vibrator apparatus or device 10, which is constructed as an eccentric vibrator device in this illustrated embodiment. This vibrator apparatus 10 is mounted on a transportable carriage 11 which is situated externally to the thermally insulated preheat chamber 5.

Hot gases arise in the melting-down operation in the melting orfoundryfurnace 2. The melting furnace 2 is heated by a gas or oil burner and is constructed as a hearth furnace and usually continuously operated such that a remainder of melt or molten metal is aiways present in the furnace or melting chamber. These hot gases are drawn off by a hot gas recirculating blower 26 through the exhaust gas conduit 20 into a ring circulation or recirculation system schematically illustrated in Figure 2.

Discharge nozzles 21 are formed in the walls of the insulated preheat chamber 5 in the form of slits through a constriction of the hot gas supply conduit and which direct the hot gas at high-velocity directly toward the aluminium scrap 8 to be preheated, as is indicated by the arrows. These discharge nozzles 21 in the preheat chamber 5 can also be constructed as round nozzles or oval nozzles.

The scrap metal 8 is uniformly distributed by the vibratory motion emanating from the vibrator apparatus or device 10. An improved heattransferbe- tween the scrap metal 8 and the hot gas impinging thereupon takes place. After a time interval of about thirty minutes, depending on various parameters such as charge size, hot gas temperatures etc., the scrap metal is preheated to about 400" to 4500 Celsius.

The carriage 11 is provided with a drive or powered drive means 14 connected with the charging bin 6 through the vibrator apparatus 10 or eccentric device. After opening doors 16 of the charging apparatus and a melting or foundry furnace door 17, the charging bin 6 is transported into the melting orfoundryfurnace 2 conjointly with the carriage 11 such that its forward region, as indicated in dotted line, extends into a melting chamber 15 of the melting furnace 2. The preheated scrap metal 8 is uniformly distributed upon a hearth 28, respectively in the melt or molten pooi of metal of the melting furnace 2 by the vibratory motion of the charging bin 6 and a simultaneous reverse or return motion of the slightly sloping charging bin 6.Both apertures or slots arising due to the transport of the charging bin 6 with the carriage 11 are each automatically closed by two sealing flaps or strips as the charging bin 6 is advanced and retracted.

It is important that the scrap metal 8 does not melt before being charged into the melting chamber 15.

Therefore the temperature of the hot gases conveyed into the preheat chamber 5 by the recirculating blower 26 must be precisely regulated. In order to optimally exhibit the heat and heat regulation, hot gas from the upper region of the preheat chamber 5, as indicated by the arrows 13, is also withdrawn and, according to Figure 2, conducted to a mixing system 23 present in the ring circulating system. Atemperature of the hot gas of about 600" to 6200 Celsius is regulated with this recirculated gas which is cooler after having surrendered its heat to the scrap metal 8.

If necessary or desired, fresh air, whose amount can be regulated by a damper valve 27, can be introduced through a supply conduit 30. The mixture of the exhaust gases from the melting or foundry furnace 2 with the hot gases withdrawn from the preheat chamber 5 takes place in this recirculating system in dependence of the hot gas temperature as measured at the entry side of the preheat chamber 5.

The excess hot gases from the preheat chamber 5 are conducted away through a stack or chimney 29 which possesses a suitable pressure regulation device 31 equipped with a regulatable damper valve 32.

The rapid preheating according to the invention not only effects a conservation of energy through more economical exploitation of the exhaust gases of a melting or foundry furnace, but the basic task of the melting or foundry furnace, namely to meltdown as great a quantity of metal as possible in a short time, is decisively improved.

The charging apparatus according to the invention is not limited to melting-down scrap metal of aluminium and its alloys. An apparatus of this type can also handle, for instance, copper alloy or zinc alloy scrap metal.

Claims

1. A charging apparatus for a melting furnace for melting-down non-ferrous metal scrap1 especially aluminium scrap, said charging apparatus comprising an integrated preheat chamber, a charging bin arranged within said preheat chamber and serving as an accumulator bin for accommodating metal scrap introduced into said accumulator bin through a chute, nozzles being provided in said preheat chamber for blowing high-velocity hot gas from an exhaust gas conduit of the melting furnace directly onto said metal scrap for preheating the metal scrap and means being provided for transporting said charging bin out of the preheat chamber into the melting chamber of the melting furnace being arranged immediately subsequent to the charging apparatus.

2. The charging apparatus as defined in claim 1, wherein said transporting means comprises a driven carriage for transporting said charging bin.

3. The charging apparatus as defined in claim 2, wherein said carriage is arranged externally of the preheat chamber.

4. The charging apparatus as defined in claim 3, wherein a vibrator device is mounted on said carriage and operatively connected with the charging bin.

5. The charging apparatus as defined in claim 4, wherein said vibrator device comprises an eccentric vibrator device.

6. The charging apparatus as defined in one of claims 1 to 5, wherein the said exhaust gas conduit of the melting furnace, a hot gas exhaust conduit for the preheat chamber and, if desired, a fresh air supply conduit open into a hot gas mixing system and wherein a hot gas recirculation blower is arranged subsequently to said hot gas mixing system.

7. The charging apparatus as defined in claim 6, wherein said hot gas mixing system includes a temperature regulation device actuating an adjustable damper valve arranged in said fresh air supply conduit.

8. A charging apparatus for a melting furnace for melting-down non-ferrous metal scrap substantially as described hereinbefore and as illustrated in the accompanying drawings.