DE2014043A1 - Melting furnace and method for melting meltable materials - Google Patents

Description

PATENT LAWYERS ^ U 1

Dipl.-Ing. EIDENEIER Dipl.-Chem. Dr.RUFF Dipl.-Ing. J. AT ER

7 STUTTGART 1 Neckarstrasse 50

Telephone ■■■■■■ 22 7O 51

23o March 1970 R / Pi

Applicant: Columbia Gas System Service Corporation

120 East 4lst Street

New York N.Y.

United States

A 12 499/500

Melting furnace and method for melting meltable materials

The invention relates to the melting of meltable materials with hot gas, the material to be melted being fed in countercurrent to the combustion products. ,

Known methods of melting fusible materials, scrap metals in particular, such as scrap iron and steel, are long, require complex devices and are not powerful »The melting of this type has been hitherto mostly made in electric smelting furnaces, blast furnaces or cupolas. Electric melting furnaces are for that too expensive for most smelting purposes, and if certain metals are to be smelted, blast furnaces need and Cupolas additionally coke together with the

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zendeii starting material. When certain hydrocarbon fuels, In particular, natural gas is added to a cupola or blast furnace containing coke, the coke prevents generally complete combustion of the oil, which results in a loss of heat. The high cost of Coke and the extra work associated with it and the high costs for the necessarily complex melting facility, led to the development of melting furnaces that generated the necessary heat with the sole consumption of liquid or gaseous fuels such as natural gas, petroleum and heating oil. However, since the previously used Layers of coke, which formed a base for the feed material inside the shaft, were needed for the new installations other documents, such as inert materials, retaining walls or retaining grids, all of which made the operation more expensive.

In the melting technology, countercurrent melting furnaces are also known, in which the hot combustion gases are passed upwards the feed material are fed and the feed material is fed down through the furnace shaft, during the lower part of the feed material is melted. Countercurrent melting furnaces that only use gaseous fuels, A have been developed, most of which are flame furnaces, where a pool of molten material remains at the bottom or in an adjacent crucible. Flame furnaces have low Melt throughputs and are inefficient, often their thermal efficiency is only 10 percent.

Bridging or sticking of material in the furnace shaft is a common recurring problem in countercurrent smelting of metals without the use of coke, particularly where a sea of molten feed material is persistently in the shaft. Bridging and sticking occurs when pieces of the feed material to melt prematurely in the shaft above the melting zone and to adjacent pieces ·

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of the feed tube as being welded or fused. When a number of pieces are connected in this way the whole of the feed material can become clumped in the chute and its continuous movement downwards be hindered. Had in previous fusion processes the layers of coke prevent this welding or melting of the feed materials. In proceedings, in where no coke is used and the feed level is arbitrary is increased high, the larger weight leaves the feed pieces compress with greater force in the lower part of the shaft β This in turn increases the chances of bridging Because of this effect, the feed height used in countercurrent coke-less furnaces has become general limited to approximately 6 feet or less. Even if the heat supply is increased per unit of time, accordingly, the bridging tendency increases, consequently the capacity and efficiency of the previous coke-less countercurrent melting furnaces were significantly limited.

According to the invention are fed to a furnace shaft Fusible materials are melted by being hot, gaseous, essentially completely burning Products in the form of a stream or beam with high Speed can be directed into the bottom of the furnace shaft. The temperature, composition and speed * speed of the jet are kept under control and its cross-sectional dimensions are selected so that the feed material is rapidly heated and melted in a localized zone at the bottom of the shaft. So will the quality of the gas jet kept under control, so that the hot gas jet within this small melting zone is cooled enough to melt further up in the shaft because of the disadvantages mentioned above

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to avoid. When the feed material melts, the molten material continuously carried away from the feed material and removed from the furnace. At the distance For example, the outflow direction of the molten material can initially advantageously run countercurrent to the combustion products, so that overheating of the molten material is achieved and thus the outflow through a suitable pouring hole is facilitated.

According to the invention, the furnace for melting meltable materials generally has a vertical or inclined shaft for damming up the feed material to be melted. The lower part of the shaft bore is like this designed to facilitate the downward movement of the feed material. The bottom of the hole is shaped so that the outflow of the molten feed material is fed to at least one exit opening on the side of the bore will. A combustion chamber and an associated burner are provided, which ensure an essentially complete combustion of a fuel-air mixture in the combustion chamber. works. A gullet-like passage connects the combustion chamber and the shaft at the drainage opening with each other, the passage being adapted to allow a high velocity jet of combustion gas from the combustion chamber flows into the shaft. Finally, a tap hole is provided through which essentially the all molten material can be removed from the shaft immediately after melting.

Melting in the countercurrent furnace according to the invention takes place quickly with significantly higher thermal efficiencies than in previous melting furnaces of comparable size. The feed height can also be increased without causing bridging in the shaft.

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In the drawing show:

Fig. 1 is a longitudinal section through the center of a melting furnace constructed according to the invention;

Figure 2 ₀ shows a longitudinal section of the empty furnace taken along the line 2-2 of FIG. 1;

3 along a partial cross-section of the empty furnace Line 3-3 of Fig. 1 and

Figs. 4,5,6, T

other embodiments of the shaft bottom in which multiple burners are used «,

Figures 1, 2 and 3 show a vertical shaft furnace according to the invention, which is used as a melting device for ferrous metals. In FIGS. 1 and 2, the furnace shaft has an outer casing, preferably made of steel, consisting of an upper casing part 13, a lower casing part 15 and a base plate 17. The upper casing part 13 is cylindrical and forms the part of the shaft which are charged with the fusible feed material and escape through the exhaust gases. This upper duct part is arranged vertically, although it can also be inclined if desired. The inner surface of the jacket is covered with a heat-insulating material 19, for example with a tubular, castable, refractory material based on aluminum oxide. Where m desired, two or more layers different insulation material can be used. The insulating material 19 lining the upper casing part 13 forms a uniform inside diameter over the entire length of the upper casing part.

The lower shell part 15, which is also lined with the insulating material 19, is designed with a bore which is flared outwards towards the bottom in order to facilitate the outflow of the supply material from the upper shell part.

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tern. The bottom 16 of the bore let advantageously inclined sufficiently from horizontal to direct the stream of molten material to an inlet port 20 as further described below. When in Fig. 1 and

2, the bottom of the bore is domed or substantially hemispherical to allow the flow of molten material through a throat 20 and one on the side of the Oven lying through channel 21 to guide. The through-channel 21 has a lowest point at which an outlet opening 23 is arranged for the continuous removal of the molten product. As from Fig. 1 and

3, the outlet opening 23 has another one Channel 24 in the bottom of the through-channel 21. The angle of inclination of the shaft bottom should be large enough thus essentially all of the molten product through the throat opening 20, the passage channel 21 and Austrittsöfffnuncj 23 flows out immediately after melting. In this way, no one can get to the bottom of the shaft Form enamel. The immediate removal of the molten material also beneficially reduces the chemical Interaction between gas and molten material, such as the oxidation of carbon and silicon when cast iron is melted.

As shown in Fig. 3, the passage 21 connects the bore of the lower shell part 15 with two combustion chambers 25 (only one visible) of the burner devices 27. The burner devices 27 are attached at an angle to one another on the side of the lower casing part 15, so that the axes of the burners form a point of intersection in the passage 21. The passage channel 21 widens at the outer end opposite the shaft like a funnel to remove the converging combustion gases from the

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to direct both combustion chambers 25 into the shaft. One Viewing opening 28 between the burner devices allows observation of the Schraelzvorgangs.

Each of the burner devices 27 consists essentially from a fuel inlet 29, an air inlet 31, a Air pipe 33, a mixer 35 with helical guide vanes, a flame holder 37, a burner liner 39 and a burner housing 41 which is lined with the insulating material. One of the burners is with one Ignition device 43 is provided, which extends through the burner housing 41 and the insulating material 19 to a point j | between the helical mixer 35 and the flame ^ holder 37 extends. Both the flame holder 37 and the burner liner 39 are made of refractory material such as zircon.

The incoming air is passed through the wing mixer 35 attached to the end of the air tube 33. The helical blades of the mixer 35 impart turbulence to the incoming air, thereby thoroughly mixing the air with the incoming fuel which is introduced into the turbulent air stream through the end of the blade mixer. In operation, the fuel-air mixture is ignited by the ignition opening -is 43, and the m resultant combustion flame is maintained in the combustion chamber 25 by a well-known in the art the manner of a flame holder 37th The burner device 27 is dimensioned and constructed in such a way that an essentially complete combustion of the fuel-oxygen mixture takes place within the combustion chamber 25. In this way, only the gaseous products of the essentially complete combustion can pass through the escaping molten metal and into the shaft.

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The fuel used has the required combustion temperature for a particular melting process. · Any hydrocarbon fuel can be used, such as natural gas, petroleum and heating oil. The most desirable fuel in terms of cost, availability and versatility is natural gas. Natural gas was particularly successful in melting various iron scrap mixtures in a melting furnace according to the invention. The fuel is preferably mixed with air or with air and oxygen to form the combustion mixture. In some cases, the air can be preheated before niche.

Advantageously, the essentially complete takes place Combustion of a preferably nearly stoichiometric mixture of fuel and air before the combustion gases come into the furnace shaft, and preferably before the Brush combustion gases over the emerging molten material. So you can get the maximum »heat of combustion get out of the fuel and in this way increase the efficiency. In our case it is supposed to be essentially complete Combustion means that in the combustion of the fuel-air mixture no more than about 2 percent combustible substances or 2 percent oxygen in the combustion gases lag behind. In an advantageous version for «» The combustion gases are regulated so that there are approximately 0.4 to 0.8 percent combustible substances and almost 0.0 percent oxygen result.

The passage 21 and the throat 20 through which the combustion products are dimensioned so that a stream of combustion gases is formed at high speed and from the combustion chambers 25 into an area or zone 40 immediately adjacent to the throat opening 20 flows. The through channel has its own for this purpose

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Smallest cross-section at or near the pharynx 20 The smallest cross-section of the through-channel or the Throat opening is much smaller than the cross section of the shaft · In the most advantageous embodiment is the ratio of the manhole cross-section to the smallest cross-section of the through-channel is approximately 8: 1, although a Ratio on the order of 4: 1 to 20: 1 applied depending on the type of feedstock, torch size, and other operational considerations. The current or jet of combustion gas generated at the 'throat opening 20' at high speed allows a high degree of heat transfer in the adjacent feed material. This creates rapid melting of the feed material in the confined or peripheral or impingement zone 40. The remainder of the The shaft acts as a preheater. Because the melting takes place in a small, limited area near the bottom of the shaft is limited, the bridging or stalling of the metal feed in the shaft is reduced to a minimum and the feed height can be increased

The passage 21 and the hot gas jet is also advantageous » adherent to the edge zone or limited melting zone in a · «sub shaft bottom and the feed material to be melted downwardly inclined angle. This prevents not only the accumulation of feed material and slag in the Passage 21 but also prevents the gas jet flows up through the shaft and helps; the Scheelaen towards the small zone near the shaft floor restrict·

Di · speed of the current flowing into the shaft. or the jet of combustion gas is greater than approx. 30 " per second and less than 300 "per second, the feed material will melt. The gullet is the gullet

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20 and the passage 21 dimensioned for speeds of this order of magnitude. Preferably at speeds from approx. ' 60m to 90m per second worked If the speeds are lower than approx. 30m per second, If the feed material melts too slowly, the metal tends to oxidize, there are carbon and silicon losses higher (when melting iron and steel) and the efficiencies are significantly lower. At speeds over There is generally excessive noise around 300 meters per second, droplets of molten feed material are easily blown up into the shaft and the drain of the escaping metal is delayed. However, at gas flow velocities in the given order of magnitude, the heat in the shaft is transferred quickly and has an effect and more can be melted in the limited melting zone 40 than in other similarly sized furnaces.

The final velocity of the combustion gases depends on the selected heat input per unit of time, and the extent of all melting work to be carried out in the furnace must be taken into account before the cross-sectional dimensions of the throat opening and the passage channel are selected. Please note, however, that there are prefabricated fires » Fixed inserts used to reduce the size of the throat if you need a higher speed for a certain melting work, it romps with you the original size of the pharynx opening is possible · Diet · Inserts can be changed as needed with a minimum of Effort to be removed and reinserted · Other means of altering the cross-section of the throat or passage may be used, including mechanically changeable devices

For larger ovens, such as those shown in Figures 4, 5, 6 and 7, can have more than one jet of combustion gases at intervals

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can be introduced into the bottom of the shaft in a distributed manner, and the molten metal can be removed through one or more throat or outlet openings. However, the shaft bottom must then be designed in such a way that individual streams of molten feed material are fed to the corresponding gullet or outlet openings v. earth. It will be understood that, according to the invention, one of the primary aspects is the melting of fusible materials with jets of combustion gas which target limited melting zones or. Areas of the feed material are directed. The molten material may cus the melting zone or zones by means of separate outlet openings or channels are removed, not necessarily erzeuejenden with one or more combustion gas jets of high velocity throat openings in communication z \\ need be. If more than one gas jet is used, tie around the duct circumference should be arranged so that each jet performs its own melting function, essentially independent of the other jets. If this is not done, bridging is more likely to occur and overall efficiency may decrease.

4 shows a further embodiment in which two separate gas jets come into the shaft through the passage channels and throat openings 20 and in two separate ones apart zones 40 cause localized melting. The molten material passes through the Durchgfingckrnjile 21 and the converging exit openings 45 from.

Fig. 5 shows an embodiment in which also two separate hot gas jets are used, but the molten material passes through one directly through the furnace wall Exit opening 47 leading into the shaft bottom is removed

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which is not connected to the through-channel 21. The gullet openings 20 * are slightly raised from the shaft bottom, so that the melted material down to the Exit opening 47 and does not flow out through the through-channel 21. The through channels 21 can also according to be inclined towards the bottom of the shaft to prevent molten material from flowing into it · When the material melted in zones 40, it flows a short distance ke downwards and exits through the outlet opening 47.

6 and 7 show further embodiments in which three separate hot gas jets can be used. In FIG. 6 the outlet opening is located in one of the lateral through-channels and in FIG. 7 the outlet opening extends into the central through-channel. As well in Fig. 6 as well as in Fig. 7 are the throat openings 20 ' something connected to the shaft above the shaft bottom, and their passage channels 21 may each be inclined downward so that molten material does not flow into the channels. The shaft bottom is in every embodiment designed to direct the stream of molten material to exit port 20. The outlet opening 20 and the slightly raised gullet openings 20 * are far enough apart to form independent melting zones but close enough to one another to prevent the molten material from solidifying before it reaches the exit opening 20.

In the melting process, the furnace is preheated in stages until the refractory lining has reached a predetermined temperature. The air and gas for the burners are adapted to the desired heat supply per unit of time and the air-gas mixture, and the shaft is

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desired height filled with feed material. The size the opening of the pharynx is selected before the beginning so that the Combustion gas jet has the desired high speed removed. The hot ones, melted over the exiting Combustion gases that spread material overheat the material easily and maintain its flowability. The at « Melting of scrap iron, normally formed slag · is removed with the molten feed material and can then be separated from the metal at an appropriate time by conventional methods · that from the Furnace coming molten material can also be directly separated furnaces for subsequent superheating or other Treatments are delivered.

The heat supply to the furnace is controlled by measuring the fuel flow with a flow meter. The air or oxygen is supplied by a positive displacement fan. The air or oxygen flow is automatically kept under control at the desired ratio · Normally the fuel flow is on the required · Amount placed in a hot but empty furnace, and the amount of air adjusted so that approx. 0.4 to 0.8 percent combustible substances in the combustion products available. If desired, the gas temperature can be can be increased by preheating the combustion air

example

A feed material made up of 30 percent steel pins from railroad tracks, 40 percent pig iron and 30 percent scrap was lifted to about 9 feet in the furnace filled up. The upper shaft part of the furnace had one

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uniform inside diameter of approx. 45cm (18 inches) The bore of the lower part of the shaft was about 1.20 m high (46 inches) and expanded outward to a diameter of about 60cm (24 inches). The shaft bottom was essentially hemispherical about 60cra (24 inches) in diameter. The cross-section of the. With the The throat opening connected to the lower part of the bore was approx . the Heat input was approximately 500,000 kcal (2 million BTU) ™ per hour and the air was not provided The fuel was natural gas. A melting rate of approx. L, lto (2,430 pounds per hour with an overall efficiency of 62.3% was achieved. The efficiency of the melting process was determined from the heat content of the removed metal and the heat of combustion of the fuel burned. During melting, the speed became the Combustion gases through the throat opening at approx. 60 » held per second. A heat input of about 750,000 kcal (3 million BTU) per hour resulted in a melting range of about 1.73 tons (3820 pounds) per hour in equals Oven·

™ The melting furnace according to the invention has saw-rich distributions, which means simplicity of basic construction and maintenance is concerned. The oven can be of any suitable size and therefore offers a variety of possible uses « Smaller versions of the furnace can be used for scrap metal smelting in emerging industrial countries, where the use of large blast furnaces or Cupola is impractical · Because of its simplified Construction, the furnace can be installed faster and cheaper

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are installed as currently available melting furnaces, which generally have high initial costs, high operating costs and relatively low efficiencies.

Dl · supply level that can be accommodated without - caused bridge is significantly larger than conventional counter-current furnaces. The greater height ensures ''. for better efficiency, since the heat of combustion; is nutet in "pre-heating the feed material completely excluded ^'J> \ and is not lost from the top of the furnace shaft ·. The feed height in each individual situation depends, for example, on the properties of the feed material and on the dimensions of the furnace itself.

• The overheating of the furnace through the passage 21 leaving molten material to, for example, about 55 ° C (100 ⁰ Fo) above the melting temperature ensures an unimpeded outflow through the outlet opening. A part of the combustion gases flows with the emerging molten materials through the outlet opening and contributes to the fact that the material remains in an overheated state, which facilitates the subsequent treatment. The degree of superheating can be changed depending on the particular feed material to be melted and depending on the intended post-treatments.

The furnace according to the invention does not require a retaining device, Baffles or inert filling materials to support the feed material in the shaft. He can melt everyone fusible materials including ores, metals, glass and minerals are used and is special effective in melting iron and steel scrap using natural gas as fuel.

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Claims (1)

A 12 499/500 - 16 - Expectations 1. Method of melting fusible materials, thereby characterized in that the materials are fed in with the formation of a longitudinal feed, forming at least one jet of hot gas at at least one end of the charge on the outer surface thereof an impact zone and the beam has a sufficient speed and temperature to allow the material to be fed into the impact zone α locally limited to melt and the remaining part ■ just preheat the feed after the end and keep the molten materials continuously away from the feeder at a rate sufficient to prevent a melt pool can form at the end of the feed. 2. The method according to claim 1, characterized in that the 'charge is arranged substantially vertically and a hot gas jet is directed at the bottom part of the charge. 3 · The method according to claim 2, characterized in that a zone for removing the molten materials is provided, which is lower than the Bodon part the loading and the impact zone. 4. The method according to any one of the preceding claims, characterized in that the hot gas jet is formed by combustion of a fuel-oxygen mixture · in at least one combustion zone, "it dec feed is in communication, but it is held by its bottom part at a distance and gaseous Ver 009842/1186 A 12 499/500 - 17 - combustion products through a narrowed passage channel be directed so that the hot gas' at a The end of the feed. « 5. The method according to any one of the preceding claims, characterized characterized in that the cross section of the jet is substantially smaller than the cross section of the feed is. 6. The method according to any one of the preceding claims, characterized in that the speed of the jet -m is greater than about 30m per second and less than about 300m per second. 7. The method according to any one of claims 4 to 6, characterized in that a hydrocarbon is used as fuel. 8. The method according to claim 7, characterized in that natural gas is used as fuel. 9. The method according to any one of claims 4 to 8, characterized in that the fuel-oxygen mixture is combusted in the combustion zone so that a schs takes place in the essential W loan complete combustion of the Gern! Before the gaseous combustion products enter the impingement of the feed . Process according to one of Claims 4 to 9, characterized in that the molten materials are removed on a path running in the jet almost in countercurrent to the combustion products. 11 · Method ⁷ according to one of claims 4 to 10, characterized in that 009342/1186 A 12 499/500 - 18 - indicates that the fuel-oxygen mixture is burned in the combustion zone so that an essentially complete combustion of the mixture takes place before the gaseous combustion products countercurrent to (5αν.:. '.. · ■ flowing molten materials under heat be led 12.Verfahren according to any one of the preceding claims, characterized characterized in that multiple jets of hot gas impinge on at least one end of the feed, wherein the jets are spaced to form substantially independent melt zones. 13. Furnace for smelting fusible materials, characterized by a shaft for receiving a charge to be melted, which is designed to direct a charge flow to at least one end of the shaft, at least one pouring hole adjacent to the shaft bottom, devices for forming an impingement or melting zone, which are arranged between the feed and the pouring hole, means tr impingement of a hot gas jet onto the feed at one end of the shaft within the on. eff zone, wherein the velocity and temperature of the jet sufficient for providing in the impingement or melting zone% \\ melt and only preheat the rest of the charge at the end of the shaft, and devices for the continuous removal of the molten material from the shaft during the melting process in such an amount that no melt pool can form at the end of the shaft 14. Oven according to claim 13, characterized in that the BATH ORIGINAL 009842/1181 A 12 49S / 5CO - 19 - Manhole is mounted vertically and the hot gas jet can be introduced at the bottom of the shaft. 15. Oven according to claim 13 or 14, characterized in that that the lower end of the chute is arcuate so that the feed more easily reach the impact zone and the molten material easier to Spout hole can flow. 16. Furnace according to one of Claims 13 to 15, characterized in that the device for allowing the hot gas jet to impinge on the charge has a through channel inclined downwards W towards the impingement zone » 17. Oven according to one of claims 13 to 16, characterized in that that the means for impinging the hot gas jet on the charge is one at one end the narrowed passage channel communicating with the manhole and one between the end of the channel and the throat opening forming means lying of the shaft, wherein the throat opening has a has a much smaller cross-section than the shaft bore at the bottom of the shaft. ■■■■ * ^; Γ ·. ■■ ■ - '.. ■■. ■:' ■ ■ ■■ " $ 18. Oven according to one of claims 13 to 17, characterized in that that he still has at least one combustion chamber connected to the passage channel and one with the Combustion chamber connected burner device for burning a fuel-oxygen mixture in the chamber. 19. Oven according to claim 17 or 18, characterized in that that the cross-section of the passage channel to the throat BATH ORIGINAL 009842/1186 A 12 499/500 - 20 - The opening is narrowed to create a hot gas jet formed at a speed of more than about 30m per second and less than 300m per second Can be. 20. Oven according to claim 18 or 19, characterized in that the burner device is designed so that a substantially complete combustion of the fuel-oxygen mixture in the combustion chamber Takes place. ·· 21 · Furnace according to one of Claims 17 to 20, characterized in that the device for removing the molten materials from the charge has a pouring hole arranged in the through-channel at a distance from the throat opening, the throat opening on the side of the shaft at its bottom is and the shaft bottom is inclined so that the feed flows to the throat opening, and the bottom of the through channel between the throat opening and the pouring hole is inclined towards the pouring hole. 22. Oven according to one of claims 13 to 21, characterized in that the lower part of the bore of the Chute has an enlarged cross-section, so that the movement of the feed stream downwards to the impact zone is facilitated. 23. Oven according to one of claims 13 to 22, characterized in that it has several devices for impinging a hot gas jet on the charge at one end of the shaft, wherein these devices are attached at intervals so that essentially independent melting zones are created 009842/1186