WO1991010749A1

WO1991010749A1 - Method and apparatus for preheating scrap to high temperature

Info

Publication number: WO1991010749A1
Application number: PCT/US1990/007631
Authority: WO
Inventors: Vinod Kumar
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-01-10
Filing date: 1990-12-21
Publication date: 1991-07-25
Anticipated expiration: 1992-07-10

Abstract

A method and apparatus for preheating scrap to high temperature by means of hot furnace exhaust gases, with or without the assistance of additional fuel burners prior to being charged into a melting furnace. The scrap preheating station consists of a preheating vessel (1) of a steel fabricated shell with or without a lining. The vessel is closed at top by an independently mounted movable cover (5) and closed at the bottom by a set of discharge gates. Cold scrap is first charged into the preheating vessel (1) by means of a scrap bucket (35), and after the scrap is preheated, it is discharged into another scrap bucket (31) to be taken to a melting furnace.

Description

Method and Apparatus for Preheating Scrap to High Temperature

Technical Field:

This invention is used for preheating scrap to high temperature before being charged into a melting furnace. Its main application is in mini steel mills which use scrap as the main source of raw material for making steel. It is also used in integrated steel mills where scrap makes up only a part of the charge. Background

Steel making processes like electric arc furnaces, basic oxygen furnaces etc. use scrap as raw material for making steel. Depending on the process, scrap may form upto 100% of the charge. The efficiency of the melting process varies between 45 to 60% and roughly 20 to 40% of input energy goes to waste in the form thermal energy of exhaust gases which must be cooled to about 90 to 140 C by a combination of water cooled duct, infusion of cold air, water sprays, air to air coolers or a combination of two or more of these processes before these gases could be admitted to a filter baghouse for cleaning and subsequent discharge to the atmosphere. All these devices mean operating expenses and capital investment to the steel maker without any recovery of the lost energy. With the introduction of ultra high power transformers, oxy-fuel burners and intensive oxygen lancing, though melting times have been reduced but at the expense of energy cost and recovery efficiency. The exhaust .gases going out of the furnace are larger in volume and at higher temperatures; thus needing larger equipment, higher capital investment and increased operating expenses to cool them down. One of the ways to recover the wasted energy is to use the exhaust gases to preheat scrap before it is charged into the furnace. Numerous designs for utilizing the thermal energy of the exhaust gases to preheat scrap before charging in the melting furance have been made and many installed. Almost all the designs use the basic scrap charging bucket with clam shells as the vessel or container for preheating scrap. Scrap preheat

temperatures of up to 250-450 C have been reported with energy savings in the range of 30-40 kilowatt hours per ton of steel and corresponding reductions in melting time. The existing systems using scrap bucket as the container for heating scrap have many problems. As expected, since the scrap bucket is subjected to hot exhaust gases and also used for transporting and handling scrap, the life of these buckets is reduced drastically despite increased maintenance. And since these scrap buckets are not lined with refractory or other lining, it is not possible to heat scrap to high temperatures. Attempts have been made to line these buckets with refractories. If the buckets are lined with refractories, firstly it increases the weight of the buckets which in many installations goes beyond the handling capacity of the existing cranes or the capacity of the scrap buckets has to be reduced resulting in more number of charges in the furnace. This results in longer heat times and subsequent loss of production. Secondly, since the same scrap buckets are sent to scrap yard to be loaded with new charge of scrap, the refractory lining cools down to ambient temperature before the scrap bucket is returned to the preheat station. Due to repeated cycles of heating and cooling, the

refractories life is very short and results in increased expenses in maintenance of these linings. All these adverse consequenses more than offset any gains in energy recovery by preheating scrap.

Scrap bucket is a crude fabrication and due to rough handling they receive during loading of scrap with magnets, scrap being dropped in these all the time and frequent lifting by crane, the scrap buckets never retain their shape, and therefore it is impossible to provide a good seal between the bucket and the hood, and between the bucket and the container they are kept during scrap preheating period. The distorsion of these buckets gets worse when these are used for preheating scrap. The biggest casualty on these buckets are clam shells on which the scrap rests during preheating. As the hot gases pass through and around these clam shells during the preheating period, these suffer most damage and need extensive repairs.

To summarize, as stated earlier, with the available designs, it is possible to preheat scrap only up to relatively low temperatures and the cost of energy saved by existing designs has been more than offset by the increased equipment and maintenance costs. Though scrap preheating is a good and economical idea, but due to the lack of a good, practical, and problem free design, it has not found vast application in industry. Disclosure of invention:

This invention comprises the following main components:

a. A scrap preheating station consisting of one or more stationary

preheating vessels, with or without refractory, metallic or other lining, which receive scrap from a scrap bucket and hold it (the scrap) while it is being heated by hot exhaust gases. After the heating cycle is complete, the scrap is discharged into an empty scrap bucket ready to receive the preheated scrap from the preheating vessels. b. A cover for each vessel which covers the preheating vessel while the scrap is being preheated in it. The cover is also used to convey hot gases to or from the preheating vessel. c. A set of bottom discharge gates for each preheating vessel which support the scrap during loading and preheating period and open by mechanical or hydraulic devices or a combination thereof to discharge scrap into an empty scrap bucket kept below the preheating vessel. d. A hot gases supply and return system with at least one set of

connections to near the bottom of the preheating vessel and the other connection either to the top of the vessel or to the cover of the vessel. If necessary, additional fuel burners can be installed either in the supply duct or in the cover to provide additional energy for heating the scrap. e. Existing or new building where the scrap preheating apparatus is installed. Description:

Figs 1, 2, 3 and 4 show typical cross sections, and Fig 6 a general

arrangement of different embodiments of alternate designs of the major components of the invention. The different components shown on these figures can be used in any combination and are not limited to the

combination shown on any of these figures. Also the scope of invention is not limited to the designs shown on these figures but also covers the scope as described in this application. Fig 5 shows the end view of a typical installation of the invention as further elaborated by description in this application. The scope of the invention is not limited to this layout only. This figure being the end view shows one preheating vessel; the scope of the invention also includes multiple vessels in parallel or in series. This figure shows the vessel is installed in a separate building. The scope of the invention provides that space, physical conditions and clearances permitting, the preheating vessel and apparatus could be installed in an existing melting furnace building also as covered in the text of this application.

Each of the major components with its specific design features is decribed below.

Scrap Preheating Vessel: The scrap preheating vessel 1 in Figs 1,2,3,4 and 6 is a steel fabricated shell with or without refractory, metallic or other lining 2 in Figs 1,2,3 and 4. In the preferred embodiment, the preheating vessel is circular in section but could also be elliptical or other shapewithout in any way affecting the intended performance of the invention. The walls of the vessel 1 are preferably conical, with larger diameter on the bottom, as shown in Figs 1,3 and 4, or cylindrical (not shown), or a combination of conical and cylindrical forms as shown in Fig 2. In another embodiment, the bottom part of the preheating vessel 1 could also be an inverted cone as shown in Fig 6, should it become necessary to discharge scrap into a smaller scrap bucket - again without affecting the intended performance of the invention. The preheating vessel 1 itself is open at the top as well as at the bottom.

The size of the preheating vessel depends on the quantity and quality of the scrap to be preheated in one batch, the size and physical dimensions of the scrap bucket and the melting practice used in the furnace.

The preheating vessel 1 is supported by structural beams 3 in Figs 1,2, and 5. The support could be mounted directly on the beams 3 as shown in Fig 1, or on spring pads 4 in Fig 2. The advantage of mounting on the spring pads 4 is that as the scrap expands when it is being heated the vessel will be lifted up thus causing less mechanical damage to the lining 2, if installed, and also less stresses in the preheating vessel shell 1. The support beams 3 could be located near the top of the vessel as shown or anywhere along the height of the vessel to suit the space and design requirements of a particular application.

The Vessel Cover: The vessel cover 5 in Figs 1,2,3,4,5 and 6 is a steel fabrication with or without a lining 6, The cover is preferably of dome shape but other shapes and forms shall also perform equally well. In the preferred embodiment, the gas duct shall be connected to the center of the top of the cover which would result in even and uniform distribution of gases over the surface of the scrap. But, if the building height and the crane approaches so dictate, the duct could be connected to the side of the cover, as shown in Figs 2 and 6.

The cover is supported from a self propelled travelling car 7 in Fig 5, which travels on tracks mounted on the support structure 3. The car has cover lifting means 8 in Fig 5, to lift and lower the cover. When the scrap is to be charged into the vessel, the cover is lifted and moved out from the top of the vessel 1. The direction of movement of the cover 5 is dictated by the physical layout of the installation. In the preferred embodiment, the cover 5 moves perpendicular to the direction of the crane travel in order to keep the building height to a minimum. Depending on the space availability and other constraints, the cover could be supported from a cantilever beam or a jib crane (not shown) or other devices. In the preferred embodiment, a gasket 9 in Figs 1,2,3 and 4, or seal (not shown) is provided between the vessel 1 and the cover 5 in order to prevent leakage of outside air into the preheater. The gasket or seal is not absolutely necessary. Bottom Discharge Gates: The basic concept of the design of the bottom discharge gates of this invention is that the hot gases do not pass through the bottom discharge gates or around them. Also the gates are opened or moved out from below the vessel 1 by mechanical or hydraulic devices or a combination thereof. The gates are closed by gravity or electro-mechanical or hydraulic means or a combination thereof.

The designs of five different embodiments of bottom discharge gates are shown on Figs 1,2,3,4 and 6. However, the scope of this invention does not only cover the particular designs shown on the these sketches but also variation of these designs in which,

a. the gases do not pass through or around the gates and

b. the gates are opened or moved out from under the vessel by electro - mechanical or hydraulic devices or a combination thereof.

Fig 1 shows the design of one embodiment of the bottom discharge gates. A pair of swing gates 11 are mounted on fulcrum pins 12 which are mounted on brackets on structural beams. In this particular embodiment, it is quite possible that these brackets could be mounted on the vessel 1 itself . The swing gates 11 are sealed against the bottom flange of the vessel 1 by a gasket seal 10. The gates 11 are swung in position to close and seal the vessel against leakage by moving in a pair of cars 13. The cars 13 are moved out to open the gates 11 and discharge the scrap in the scrap bucket below after it has been preheated. The cars movement is accomplished by a withdrawing device 14 comprising hydraulic cylinder or electro-mechanical device or a combination thereof. The cars 13 are equipped with a set of spring pads 15, which exert continuous pressure on the swing gates 11 to keep them sealed against the bottom flange of the preheating vessel 1. When the gates 11 are to be opened, a set of gates sealing hydraulic cylinders (not shown) relieve the spring pressure, so that the cars 13 can be moved out and the gates 11 automatically opened. When the gates 11 are to be closed, the gates sealing hydraulic cylinders keep the spring pads 15 depressed, the cars 13 moved in position and then the gates sealing hydraulic cylinders are depressurized to let the spring pads 15 exert pressure on the gates 11 to keep these pressed against the bottom flange of the vessel 1.

In another embodiment of the same design (not shown), the pair of the cars 13 are replaced by a set of hydraulic cylinders or electromechanical devices which swing the gates 11 in and out. And by means of

accumulators in the hydraulic circuit or torque limiters in the electro- mechanical device, constant pressure is exerted on the swing gates 11 to keep the seal tight.

Fig 2 shows the design of another embodiment of bottom discharge gates. In this embodiment, the bottom discharge gates consist of a pair of travelling cars 16 made of heavy fabricated steel structure. Each car has an upper frame 17, fully detachable from the main frame 16. The upper frame 17 is also made of heavy steel fabrication with top surface with or without cast iron or other heat resistant steel liners and act as the bottom discharge gate. The upper frame 17 is moved up and down in slides in the main frame 16 by a gates sealing device 18, which serves to seal the upper frame 17 against the bottom flange of the vessel 1 through a gasket 10. The gates sealing device 18 consist of either a set of hydraulic cylinders or electro- mechanical drive. When the bottom discharge gates are closed, the gates sealing device 18 exerts constant pressure against the bottom flange of the vessel 1 in order to provide a good seal and prevent air infiltration. The travelling cars 16 together with the upper frames 17 are moved in and out by a withdrawing device 14 consisting of a set of hydraulic cylinders or electro-mechanical drive or a combination thereof.

When the preheated scrap is to be discharged, the upper frames 17 are first lowered by releasing the pressure of the gates sealing device 18. This removes the seal between the bottom flange of vessel 1 and the upper frame 17. Now the withdrawing device 14 is activated to move the travelling car 16 together with the upper frame 17 from under the preheating vessel 1 thus discharging the preheated scrap from the vessel 1 into the scrap bucket below. In order to prepare the vessel 1 to receive the new charge of scrap for preheating, the travelling car 16 -with the upper frame 17 in the lowered positon is moved under the preheating vessel 1. When the car travel is complete, the vessel sealing device 18 is activated which then lifts the upper frame 17 against the bottom flange of the vessel 1 and seals the preheating vessel. The vessel 1 is then ready to receive the new charge of scrap. The front face of the upper frame is equipped with a seal to prevent air infiltration along the face of the two upper frames.

Fig 3 shows the design of another embodiment of bottom discharge gates. In this embodiment the bottom discharge gates consist of a pair of travelling cars 16, of heavy fabricated steel construction, which travel on a track mounted on support frame 20. The cars are moved in and out by a withdrawing device 14 which consists of a set of hydraulic cylinders or electro-mechanical drive or a combination thereof. The outer end of the support frame 20 is hinged while the inner end is moved up and down by a gates sealing device 18 which consists of a set of hydraulic cylinders or electro -mechanical drive or a combination thereof. In the preferred embodiment, the top surfaces of the cars are lined with cast iron or other heat resistant steel liners which seal against the bottom flange of the vessel through gasket 10. The pair of cars 16 act as the bottom discharge gates. When the preheated scrap is to be discharged, the support frame 20 is lowered by releasing the gates sealing device 18. In the lowered position the support frame rests on stops 21. This provides better support and rigidity to the support frame 20 and also the bottom discharge gates. The travelling cars 16 are then moved out by the withdrawing device 14, thus discharging the scrap in the the scrap bucket below. In order to prepare the preheating vessel to receive a new charge of scrap, the travelling cars 16 are first moved in below the preheating vessel 1 by the withdrawing device 14 and then the gates sealing device 18 is raised to push the travelling cars 16 against the preheating vessel 1. The vessel 1 is then ready to receive a new charge of scrap. During the preheating period, the gates sealing device 18 maintains continuous pressure on the travelling cars 16 to keep them sealed against the bottom flange of the vessel 1 and thus prevent any infiltration of outside air.

Fig 4 shows the design of yet another embodiment of the bottom discharge gates. In this embodiment, the bottom discharge gates also consist of a pair of travelling cars 16, Each car 16 has an upper frame 17, which is pivoted on the main frame 16, The pivoting of the upper frame takes care of any misalignment between the bottom flange of the vessel 1 and the surface of the upper frame 17, the car 16 itself or the car travel track 20 and thus results in a more effective seal. The travelling cars 16 themselves together with the upper frames 17 are moved in and out on a support frame 20 by a withdrawing device 14 which consists of a set of hydraulic cylinders or an electro-mechanical drive or a combination thereof. The outer end of the support frame 20 is hinged while the inner end is lifted and lowered by a gates sealing device 18 which consists of a set of hydraulic cylinders or an electro-mechanical drive or a combination thereof. In the lowered position, the frame 20 rests on stops 21 in order to provide more stability and rigidness to the support frame 20 and the travelling cars 16. The seal 10, mentioned above is provided only in the preferred

embodiments and is not absolutely necessary.

Fig 6 shows the design of yet another embodiment of bottom discharge gates. In this embodiment, the bottom discharge gates also consists of a pair of travelling cars 16, of heavy fabricated steel construction, with or without cast iron or other heat resistant liners. The cars 16, travel on a track mounted on a frame 20. The cars 16 are moved out by a

withdrawing device 14 which consists of a set of hydraulic cylinders or other electro-mechanical device or a combination thereof, and a connecting means 20 like chain or wire rope, which passes over a pulley or sheave 23. The cars 16 are moved in by gravity or other means (not shown). The support frame 20 is fixed and, in this embodiment, the cars are raised to seal against the bottom flange of the vessel by a gate sealing device 18 which consists of a set of hydraulic cylinders or electro-mechanical device or a combination thereof.

The operating principle of this embodiment is also the same as described for embodiment in Fig 3.

Hot Gas Supply and Duct System: To prevent melting of scrap in preheater, the hot gases from melting furnace are cooled to a temperature below the melting temperature of steel before being admitted to the preheating vessel. As experience is gained with the operation of the preheater, hotter gases could also be admitted. Necessary dampers in the duct are provided to isolate the preheater for maintenance and during charging and discharging of scrap. An auxiliary burner system can also be installed in vessel cover or in the duct for providing additional energy for preheating the scrap, The gases are conveyed to the scrap preheater either from the duct connected to cover or through the duct connected to the bottom part of the vessel. The preferred method will be to supply the hot gases through the duct connected to the center of the cover, as shown in Figs 1,3,4and 5. This arrangement in combination with outlet duct design covered in this invention results in even distribution of gases in the preheater. This also yields more uniform and predictable scrap temperatures. In another embodiment, as mentioned earlier, the duct can also be connected to top part of the vessel (not shown). In order to distribute the gases more evenly over the surface of the vessel, the inlet duct shall bewrapped around and the gases admitted evenly along the periphery of the vessel. However this is the last resort as this increases the height of the vessel and the distance the scrap has to be dropped thus causing more impact loading on bottom discharge gates.

By proper ducting and control of the dampers, the most preferred

embodiment is to convey the gases from top to bottom for part of heating cycle and then reverse the direction from bottom to top for the rest of the cycle or vice versa. This results in more uniform and predictable

temperature of scrap throughout the height of the scrap mass. The other duct, which as stated earlier can be used either to supply or exhaust gases to or from the vessel is connected near the bottom edge of the vessel. In the preferred embodiment, as shown on Fig 2, the duct 25 runs around the periphery of the vessel 1 with calculated opening all around so that the gases are distributed evenly around the circumference of the vessel 1. The duct 25 may be lined with refractory 26. The even

distribution or collection of gases by means of this specially designed duct results in more evenly heated scrap in the vessel 1. It also yields better energy recovery. In the preferred embodiment, the duct is mounted independently of the vessel so that any movement of the vessel 1 is not transmitted to the duct 25. In order to seal the duct from the vessel, a seal 27 is provided as shown. The seal 27 is a flexible, high tempearature resistant fabric. One edge of this seal is bolted to a flange welded to the vessel 1; the other edge could be lying flat on the duct 25 as shown or could be bolted leaving some flexibility to allow relative movement between the duct 25 and the vessel 1. Since the duct is always under suction the seal 27 is always sucked against the duct 25 and thus providing a good seal. If the duct 25 is mounted on the vessel 1, seal 27 is not necessary. In an alternate embodiment, the duct 25 is mounted directly on the vessel 1 as shown in Fig 4 and 6. The duct 25 could have any cross section, square as shown in Fig 6 or round as shown in Fig 4. In order to improve gas distribution, as stated earlier, the duct 25 is run around and connected by small multiple ducts 24 around the periphery of the preheating vessel so that the gases are supplied or exhausted all around the circumference.

Depending on the physical location and constraints, the duct could be connected on one side of the vessel, as shown in Fig 3, or the single duct bifurcated and the two branches connected to the vessel diametrically opposite to each other (not shown). This embodiment will, however, not provide even and uniform gas distribution in the vessel and is to be adopted under extenuating circumstances only.

Scrap Preheater Installation and Building

The scrap preheater of this invention can be installed in many ways. The main considerations in its installation, as shown in Fig 5, are: a. A scrap bucket 31 on transfer car 32, is able to pass under the vessel 1 and allow the vessel 1 to discharge the load of scrap in it (scrap bucket 31). It should also be possible to pick up the scrap bucket 31 by an overhead crane to be discharged in melting furnace. b. A crane 36 should be able to discharge a bucket 35 full of scrap in the preheating vessel 1, and c. There should be space around the vessel 1 for the supply and return ducts for the hot gases.

These conditions can normally be met in most steel mills in which the melting furnace is located on an elevated platform; and it is mostly feasible to install the scrap preheating vessel in an existing melt shop building.

If due to logistics and space limitations, the scrap preheater and the associated equipment can not be installed in the existing melt shop, a separate building as close to the existing melt shop as feasible is to be constructed. The two buildings should preferably be connected by a short transfer car track. The cross section of the new building which is also part of the scope of this invention is shown on Fig 5. The new building 33 is of structural fabrication. Building roof and siding are not necessary but are dictated by the local climatic conditions. The installation consists of scrap bucket transfer car track 34 which receives the scrap bucket 35 loaded with scrap from the scrap yard and also lead to the melt shop. The loaded scrap bucket 35 can also be brought to and taken away from building 33 by other means of transportation. The building 33 is to be as narrow as possible; its width is dictated by the size of the preheater vessel to be installed. The building 33 is equipped with a crane or crane trolley 36 to lift the scrap bucket 35 and discharge the scrap into the preheating vessel 1. The building length is determined by the number of preheating vessels to be installed.

Method of Operation

As a part of this invention, the scrap is brought in scrap buckets 35 to the preheater installation by any of the available means of transportation. The scrap bucket 35 Is lifted by the existing crane in the existing building or by the crane or crane trolley 36 installed in the new building 33 or by other lifting means. The vessel cover 5 is lifted by cover lifting device 8 and moved away from the top of the vessel 1 by the roof removing mechanism 7. The bottom discharge gates are closed and sealed. The bucket clam shells are then opened and the scrap discharged into the preheating vessel 1. The bucket is then moved away and lowered on to the bucket carrier. The vessel cover 5 is moved over and lowered on to the vessel 1. As soon the vessel 1 is covered, the necessary dampers in hot gas ducts are opened and the flow of gases started. When the scrap is required by the furnace, an empty scrap bucket item 31 on the transfer car 32 is made available below the preheating vessel 1. As soon as ready signal is received from the furnace operator, the hot gas dampers are closed in safe sequence, the discharge gates opened and the scrap discharged into the scrap bucket 31 below. The scrap transfer car 32 is then immediately moved to where the scrap bucket 31 can be picked up by the overhead crane to be discharged into the melting furnace. The activities are closely coordinated to keep the transfer time to minimum both to preserve heat in the scrap and to expose the scrap bucket to high temperature scrap the least period of time. Once the heated scrap has been discharged from the vessel, the discharge gates are closed and the new preheting vessel loading and heating cycle started. Advantages:

This invention has many distinct advantages over the existing scrap preheating systems as listed below:

a. Since the scrap bucket is not used for heating the scrap and the preheatihg vessel can be lined with refractories or other material, the scrap is heated to much higher temperatures than possible with the existing systems, b. Since the scrap buckets are exposed only to heated scrap (not hot gases) and that too for the short duration of transfer time, there are no adverse effects on the life of the scrap buckets, c. The scrap is heated to temperatures substantially higher than

attainable with the existing systems, greater power savings per ton of steel result accompanied with shorter heat times, reduced electrode consumption and increased plant production. d. Due to scrap being used for cooling the gases, smaller fume exhaust systems are required and less operating expenses for gas cleaning plant, e. Since the bottom discharge gates are not part of the preheating vessel, and are not subjected to direct impact of hot gases, and are made of heat resistant material, these gates give long life with almost no maintenance, unlike the clam shells of the scrap buckets.

The invention is not limited to the embodiments described above, but also includes the scope set forth by the following claims, without deviating from the inventive idea.

Claims

I claim:

1. An apparatus for preheating scrap prior to charging into a melting means with the heat energy of hot exhaust gases with or without the assistance of additional heating means, wherein said scrap is first charged from a scrap transporting means and wherefrom said scrap after preheating is discharged into said or other scrap transporting means to be taken to a melting means, comprising: a. a preheating station consisting of one or more stationary containing means adapted to receive and hold said scarp during preheating, b. supporting and discharging means located below and mounted

independently or from said containing means to serve to support said scrap in said containing means and to discharge said scrap into said or other scrap transporting means when retracted from under said containing means by withdrawing means comprising hydraulic or electro-mechanical means or a combination thereof, and wherein said exhaust gases do not pass through or around said supporting and discharging means, c. covering means located above said containing means w hich are lifted and moved away from top of said containing means to allow loading of said scrap into said containing means and which are moved back, lowered and kept on top of said containing means during preheating of said scrap, d. supplying and exhausting means to supply and exhaust said hot exhaust gases to and from said containing means.

2. An apparatus for preheating said scrap according to claim 1 wherein said containing means comprise a steel shell, conical, cylindrical, or a combination thereof, or any other shape without an integral top or bottom, with or without a lining laid against said steel shell wherein the said steel shell is supported on a steel structure directly or through a set of spring pads.

3. A method for preheating scrap prior to charging into a melting means with the heat energy of hot exhaust gases, with or without the assistance of additional heating means, wherein said scrap is first charged into a stationary containing means from a scrap transporting means and then said scrap is discharged into said or other scrap transporting means after said scrap has been preheated or is required by melting means.

4. An apparatus as claimed in claim 1 wherein said supporting and discharging means comprise a set of swing gates with or without cast iron or other heat resistant liners, which swing out when a set of travelling means are moved out by withdrawing means comprising hydraulic or electro-mechanical means or a combination thereof, from under said set of swing gates thereby causing said set of swing gates to open and discharge said scrap from said containing means and wherein said travelling means move in to close said set of swing gates against said containing means and prepare said containing means to receive a new charge of scrap to be preheated.

5. An apparatus as claimed in claim 1 wherein said supporting and discharging means comprise a set of swing gates, with or without cast iron or other heat resistant liners, which swing out when a set of withdrawing means comprising hydraulic or electro-mechanical means or a combination thereof, are withdrawn thereby causing said set of swing gates to open and discharge said scrap from said containing means and wherein said withdrawing means are pushed back to close said set of swing gates against said containing means to prepare said containing means to receive a new charge of scrap to be preheated.

6. An apparatus as claimed in claim 1 wherein said supporting and discharging means comprise a set of slide assemblies with or without wheels which are moved in and out from under said containing means in a guide or on a track mounted on a support frame, by withdrawing means comprising hydraulic or electro-mechanical means or a combination thereof, wherein said set of slide assemblies consist of an upper frame, with or without cast iron or other heat resistant liner on the top surface, and a main frame.

7. An apparatus as claimed in claim 1 wherein said supporting and discharging means comprise a set of slide assemblies with or without cast iron or other heat resistant liners on the top surface, and with or without wheels, wherein said set of slide assemblies is moved in and out from under said containing means in a guide or on a track mounted on a support frame by withdrawing means comprising hydraulic or electro-mechanical means or a combination thereof; and wherein the outer end of said support frame is hinged and inner end lifted and lowered by a sealing device which comprises hydraulic or electro-mechanical means or a combination thereof.

8. An apparatus as claimed in claim 6, wherein said support frame is fixed and wherein said upper frame is mounted on said lower frame directly or on a set of spring pads and lifted to seal said upper frame against the bottom flange of said containing means by a gates sealing device comprising hydraulic or electro-mechanical means or a combination thereof and lowered to allow said set of slide assemblies to be retracted from under said containing means.

9. An apparatus as claimed in claim 6, wherein the outer end of said support frame is hinged and the inner end is moved up and down to seal said upper frame against the bottom flange of said containing means by a gates sealing device comprising hydraulic or electro-mechanical means or a combination thereof; and wherein said upper frame is pivoted near its center on said lower frame.

10. An apparatus as claimed in claim 1, wherein one or both of said supplying and exhausting means are connected to said containing means at one or multiple points around the periphery of said containing means by connecting means of calculated size to evenly distribute said hot exhaust gases used for preheating said scrap,

11. An apparatus as claimed in claim 1, wherein said supporting and discharging means comprise a set of slide assemblies with or without wheels and with or without cast iron or other heat resistant liners; and wherein said set of slide assemblies are moved in and out from under said containing means by a -withdrawing means comprising hydraulic or electromechanical means or a combination thereof, and wherein said set of slide assemblies are lifted and lowered while under said containing means by a set of sealing means comprising hydraulic or electro-mechanical means or a combination thereof.

12. A building for installation of stationary scrap preheating station for preheating scrap prior to charging in a melting means by hot exhaust gases with or without the assistance of additional heating means, comprising: a. one or more stationary preheating vessels complete with scrap

containing means, scrap supporting and discharging means, and

independently mounted and movable covering means, b. handling means to lift and handle scrap transporting means to discharge said scrap into said preheating vessels, and c. supplying and exhausting means to supply and exhaust said hot exhaust gases to and from said preheating vessels, wherein said scrap is first charged into said preheating vessels and then, after said scrap has been preheated or is required by melting means, said scrap is discharged from said preheating vessels into said or other scrap transporting means to be taken to melting means.