DE1932048A1 - Method and device for processing scrap containing iron - Google Patents

Description

PATENT LAWYERS

Dlpl.-lng. EL THE EGGS I 9 YEARS 4-8

Dipl.-Chem. Dr. RU FF Dipl.-Ing. J. BE I E R

7 STUTTGART 1 Neckarstrasse 5O Telephone 2945O7

June 23, 1969 R / Lb

Applicant: Columbia Gas System
Service Corporation

1 SO East 4-1st Street. ITew York, Ν · Υ. / UNITED STATES

A 12 134/35

Method and device for Processing of ferrous scrap

The invention relates to the treatment of or steel and in particular to the transformation of iron and steel scrap in reusable forms »

More and more scrap is available for processing into steel and the quantities used are maintained not step up with the quantities »which are available · This is largely due to the increase in Steel production with the help of oxygen according to the "basic" Oxygen Process "(Basic Oxygen Process) and the introduction of oxygen into the open furnace with oxygen lances »The main reason for this

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is that the use of oxygen both in the open hearth and in the basic kiln Si © Seit sux · generation of the heat required for the steel has actually reduced ο These processes are based on the combustion of dissolved impurities such as carbon, silicon, hangings, etc. . in the hot blast furnace metal to the necessary heat to generate · Therefore, he was transferred look more to the pig iron and blast furnace production and DE® use of scrap, which is usually relatively poor oxidizable at these additions is less importance has been attached. This is particularly true of the basic oxygen process (BOF), in which the ratio of liquid pig iron to cold scrap material is normally between 75 to 25 or 70 to 30 Use foreign wire.

So far, different processes have been used that use B- containing gases in direct contact with the liquid iron. The oldest were the Bessemer and Sßhomas converters, who use Is2 £ t as a combustion medium The process of converting lost its importance due to the nitrogen brittleness of the steel produced in this way · The injection of pure oxygen from the bottom or from the side was in a Bessemer or Shomas converter not practical because of the extraordinarily high temperatures at the points where oxygen was introduced. These severe heat accumulations occurred in the metal bath and in the areas where the bath was exposed to carbon monoside

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strong release of tfree oxidized. The development of the basic Saiieratoffverfahxein (BOP) or ED process resulted in a successful technique for the introduction of pure oxygen by applying it directly to the molten hate of one's own Oxygen or oxygen-enriched air is blown in from the floor, is found · Similarly, it is now customary to bring pure oxygen into open stoves by blowing it from above onto the bath. Oxygen-rich air is also used in overhead burners to maintain higher temperatures and to increase the heat transfer into the steel bath. This has led to a reduction in the heating time in ■ the open firing systems, but it does not allow an increased use of scrap compared to »previous work with an old open stove with a typical proportion of 50 % very soot and 50 % metal.

There is a need “to be able to produce steel from scrap by an economically feasible method, and thereby tackle this large, partially recovered hachachub of metallic iron. Various such methods have been proposed. One of these methods is a modified converter process, called "Kaldo Oxygen Stahlherstelluxigs-Yerfahren", which has the advantage that you can work with 50 % scrap and 50 % lignite. This process, however, has certain drawbacks refractory materials in the rotating vessel in which the process is carried out. Another proposed method to achieve greater use of scrap in the basic oxygen furnace is the addition of relative

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expensive fuel additives, such as calcium carbide, ferrosilicon, Silicon carbide, etc. «. This modification of the BOP process is (however, not often used due to the high cost of these additives «

Another method of obtaining a higher proportion of scrap material in relation to the pig iron is the so-called "Dual hearth", in which the F melting room of the open hearth is divided into two sections is. The sections are fired alternately.While a steel melt is being processed in one section, the hot exhaust gases are passed over the scrap in the other section, melt it and prepare it for adding pig iron and for refining.The purpose of this method is the Increase the use of scrap in the open hearth without needing the longer heating periods that are typical of the normal open hearth process with proportions of 30% raw metal and 50 % scrap

. Attempts have also been made to make a steelmaking process "to develop with preheating and melting of Sehrott In shaft or cupola furnaces * Scrap can be preheated in shaft furnaces or similar devices, but at the same time as this preheating, oxidation can occur and become very rapid near the melting point · This requires the use of gases which are strongly reducing · Because of this problem the oxidation, together with bridging and clogging of the shaft, it is usually necessary to add either coke or pig iron as a sideline to the Xupol charge »This results in a metal that has a high proportion of carbon and is therefore subsequently put in a converter furnace for steelmaking needs to be refined. _t

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Its methods of using scrap as described above are widespread, as each has one or more important disadvantages associated with it. The traditional arc furnace process is ideal, while the traditional arc furnace process is ideal, as is the widely recognized process now used to manufacture steel from scrap on a large scale for the production of alloy. stanchions and quality steels, carbon steel can be relatively expensive to produce. Furthermore, the cost of energy and electrodes can be too high to warrant introduction in small or medium-sized steel plants. In addition, the power requirements of the arc traversed are such that it is not always possible _9-arc furnace to power distribution systems to connect arc furnace "One is because of the strong fluctuations in the company not a desired power consumers would be in a re t ζ syst em _t if this system is not very big · Otherwise it is necessary to install a generator specifically for the arc furnace.

It is thus evident that there is a real need here for an improved method and apparatus for conversion from scrap to steel or other usable forms consists of · The use of either steel scrap alone or with a small amount of bohe iron provides one potentially valuable source of iron for steelmaking.

The method of the invention offers an improved one Method of converting or refining scrap iron or steel regardless of its carbon content and for conversion to usable steel with the desired carbon content. The procedure is cheap, fast and has a flexibility in the way of working. the variations and precise control of the obtained Steel composition and consequently the properties of the steel produced

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The invention can advantageously be used in connection with a pneumatic steelmaking process in one integrated steel plant that is not by the ratio limited by scrap from pig iron in the iron tubing is to be applied

The steelmaking process according to the invention is also particularly well suited for use in small non-integrated systems for the production of steel with a w low or medium carbon content from scrap ·

The invention broadly encompasses the treatment of ferrous metals, iron or steel by reacting an oxidizing agent with a fuel, preferably natural gas, beneath the surface of a molten ferrous metal. The invention is particularly advantageous in the manufacture of steel from scrap and in a steel mill as a modification of the known material process (BOP), which is particularly useful in the case of oxygen lances.

Further features of the invention emerge from the detailed description of embodiments below in conjunction with the accompanying drawings and claims.

In the drawings show:

Pig, 1 A longitudinal section of a furnace for the purpose of ^ conduct of the inventive method, taking oxygen from the surface into the Melt and deir fuel under the Melt is introduced f

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Hg. 2 a schematic representation of an entire BjBtGmB with additional facilities for StronniDgskonfcrolle the various liquids!

3 shows a longitudinal section of another embodiment of a furnace for carrying out the method according to the invention in which both the Oxygen as well as the fuel are introduced below the melt;

Jig · 4- a cross section of the bottom part of the furnace

3 along the line 4-4 of FIG. 3 $

5 shows a longitudinal section of a further embodiment of a furnace for carrying out the invention. according to the method in which both the oxygen and the fuel are introduced at the surface of the melt;

Figure 6 is a cross-section of the central part of the furnace according to Fig. 5 along the line 6-6 of Fig. 5

FIG. 1 shows an embodiment of the device according to the invention and this figure is used below to describe the method according to the invention. A furnace 10 which is used for Execution of the method according to the invention is suitable, has a vertical wall 11, which by a suitable Heat-resistant lining 12 is protected · The furnace wall faces continue to have a bulged rope 13, which with a Heat-resistant material 14 is lined · You bulge

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forms within the furnace housing a depression 15t has such a large volume that, when the furnace is rotated by approx Cover with a heat-resistant lining 19 and a bottom part 20 with a heat-resistant lining 21 · In the bottom of the furnace a number of injection nozzles 23 are provided, which enable a flow connection between the furnace and a removable fuel inlet system they are used in a known manner in the Bessemer-Sonverter process and are therefore not described in more detail.

In the furnace space 29, a molten metal 30 is shown in FIG. the scrap 31 is suspended and on the surface of which there is a layer of molten slag £ 2 »Bs it is believed that this molten slag layer possibly coalesces with the metal bath during the The process sequence is mixed because of the turbulence in the bath which, due to the high inflow speed of the oxygen, reduces the inflow speed of the fuel and causing the exothermic reaction to take place and causing splashing of the slag and a portion of the molten metal in the furnace space 29. The intimate one Creates contact of the slag with the molten metal an effective means of cleaning the scrap slag, since it eliminates the separation of oxidized impurities ζζ · Β · Silicon dioxide, manganese, zinc and refractory metals, etc. «)

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from the melt into the slag. The oven can be constructed in such a way that it is possible to place the furnace space 29 underneath To put pressure to boiling or agitation in the To reduce the melt if it is desirable

In the embodiment shown in FIG. 1, it becomes cleaner Oxygen or some other oxidizing agent is introduced through the top of the container where it is immediately in the molten ferrous metal, or with dissolved admixtures or iron with heat generation and Formation of oxides converts, which in turn is suspended or dissolved in the molten metal or the slag «This can be achieved by introducing the oxygen through oxygen lances 34- and 35, according to the known procedure, which in the basic Oxygen oven is used. These lances are common water-cooled and are, as far as they are not of conventional construction, described in more detail »The fuel is introduced into the melt below the melt using the injection nozzles »The fuel reacts with the dissolved oxygen and also releases heat to melt the scrap «What is contained in the melt Iron oxide is reduced to molten iron by the fuel gases The melt is the partial combustion of the fuel with oxygen · When more oxygen is introduced than can react with the fuel, there is a final production of iron oxide. This excess iron oxide can be chemically reduced to iron by increasing the oxygen supply decreased or the ratio of oxygen to fuel is changed in some other way to produce iron oxide to reduce chemically to iron "

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A gas outlet 37 is provided to allow the exhaust gases out the oven · The oven in Figure 1 is adjustable on shift work or "continuous" operation · When he used for "continuous" operation is an introduction for scrap, such as chute 38, at the top and a valve-controlled discharge line 39 near the bottom of the melt. The line 39 is set up to draw off the molten metal · Finally, it is like a common Bessemer pear In Figure 1, a pivot 40 is provided which on conventionally rotatable in a suitable gear and bearing

Before describing the process in detail, it will be be useful to explain Figure 2 au, which is roughly a schematic representation of the typical overall system a »» finally the furnace is and the procedure according to 4er «* Finding used · The furnace is again by the same Number 10 denotes «Same numbers in Figure 1 and in Figure 2 relate to the same items · It is It can be seen that the pivot 40 is in a suitable support and bearing device with supports 42 and a Foundation 43 is held

In so far as the exhaust gases can be used in various ways, preferably for preheating both the scrap and the oxygen and fuel, it is easiest to begin the description of FIG. 2 with the distribution devices for the exhaust gases. In Figure 2, an exhaust pipe 51 · is controlled by a valve 52, connected to a combustion chamber or heat exchanger 53 ₅ for burning the high-temperature exhaust gases (a substantial amount of hydrogen and

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ait air is arranged, which is _{introduced into the combustion chamber 53 through a pipe 54-v} controlled by a valve 55. On the other hand, the hot exhaust gases (which contain a lot of perceptible heat) can be brought into contact with the scrap and preheat it · Me burned exhaust gases can then be controlled directly by a DurchfluBrohr 56 'through a valve 57t flow therethrough · the unburnt exhaust gases on the other hand shower Bohr 58 ₁ are controlled by valve 59, in a suitable conduit überfuhrt 60, which is connected to a Gaakühler and wipers 62 is (

The combustion chamber heat exchanger 55 is preferably constructed so that it consists of a series of stacked combustion chambers each holding a limited amount of air or other oxidizing agent ^ yTfrrftPTWB g ftT w m ffl value ¹ arrives "while the exhaust gases are led upwards and burned. This leads to a disruption of a favorable distribution in the 3? eaperatü £ and in the composition of the combustion gas" since the hottest scrap is exposed to those combustion gases aa the strongest reducing are "those are the ones that germinate from the furnace, weigh the cold scrap""which enters the combustion chamber - heat exchanger" is exposed to the oxidized flue gases · This type of preheating of the scrap avoids or reduces the undesired oxidation of the scrap * ·

It is shown in FIG. 2 that the flue gases from the furnace can be routed directly to line 60 (through valve 61) with the aid of line 51, if combustion of these gases is not desired on this boaact. The choice will depend on whether whether it is desirable or not «to preheat the scrap directly, which is described below

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After the exhaust gases have passed through the gas cooler and scrubber 62, they can be discharged directly through the line 63, -or they can be directed in one or two alternative routes by suitable actuation of the valves 64 and 65. The first of these routes is over Line 66, controlled by valve 67, which leads to the main fuel line so that the unburned flue gases can be returned to the furnace. The other alternative at this point is to close valves 65 and 67, open valve 64 and let the gases in admit a Verbrennungskaamer 69, which is designed for burning the gases with air, which is introduced through line 70, controlled by valve 711 · the Verbrennungegase of the v ^{»T> 'h' n ftT | NIIR>} e ^a ^ ^r PT ^iwn f ^{> T} * 69 can then over line 72 in an indirect heat exchange rather 7? to the subsequent outlet through line 74 and similarly through a branch line 75 »controlled by valve 76, into an indirect heat exchanger 77 for the outlet through line 78. The purpose of heat exchangers 73 and 77 is to provide heat for preheating the fuel and to provide the oxygen before introducing these heaters into the furnace 10

Oxygen is supplied from a suitable source 80 which shown in Figure 2 as high pressure oxygen · Of course it is within the scope of this invention to use low pressure gaseous oxygen, liquid oxygen and to use other suitable means to vaporize it prior to its introduction into the oxygen line 81. These Oxygen line 81 leads through the heat exchanger 77 and is connected to the lance 34 which extends into the furnace "

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The fuel source 90, which is any source of a Suitable fuel is through line 91 »controlled by valve 92, with the fuel inlet line 26 connected · Line 91 leads through the indirect heat exchanger 73 for heating the fuel · Wenn If burned exhaust gases are to be routed back through the furnace, they are conveniently placed in the fuel line 91 introduced · The fuel can also be introduced into the furnace above the surface of the melt. This can be controlled via the fuel lines 91 and 93 * through valve 94 · »which happened before her Lead the connection to the upper part of the furnace 10 through the indirect heat exchanger 73 Within the scope of this invention to use a fuel mixed with some air or oxygen · To do this an auxiliary oxygen source 82 is provided which through line 83 and valve 84 · to the fuel line The oxygen or the oxygen-containing gas can of course also be supplied from the source 80 “It is also within the scope of the invention to use the heat exchanger 53 to be designed so that a direct preheating of scrap, as described above, and an indirect Preheating of fuel and oxygen by separate heat exchangers in sync with the exhaust gases direct scrap pre-heating is possible

Finally, the device of Figure 2 is suitable for preheating the scrap that is introduced into the furnace · This is achieved by passing scrap through the preheating chamber 53 before using suitable gowns, shown schematically as a line in Figure 2, into the furnace

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The device of Figure 2 is set up so that it is not necessary to choose alternatives in all cases, but it is possible to use a combination of Use preheating systems · For example, some of the exhaust gases may be introduced into the combustion chamber 53 while the remaining {Dell is being introduced into the combustion chamber 69 * This, on the other hand, would mean create both the scrap and the fuel and preheating the oxygen “Of course, it is within the scope of the invention to only preheat the fuel below the surface the melt or both below the surface and on the surface and the flow rate to vary in any desirable way in the system of Figure 2 "

The function of the furnace of Figures 1 and 2 and the inventive Procedures are referred to below described in detail on the figures

The procedure is carried out by using a best (heel) of molten steel from the previous one Melting begins with a volume adapted to the scrap additions · While scrap is added the furnace by approx. 90 ° from that shown in FIG

ί Tilted position to keep enough tree for the metal residue so that the molten metal does not come into contact with the injection _{nozzles.The initial f} scrap batch (either preheated or cold) is preferably brought into the container in the tilted position, while at the same time gaseous fuel

j via the fuel line 26, antechamber 25 and

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Nozzles 23 is blown into the oven · The oven is then in upright position inclined and the oxygen lance 34- (and possibly 33) lowered in order to blow in the Introducing oxygen · Even though Figure 1 shows two oxygen lances, as shown in Figure 2, «also only one to be used · During this start time and during Whenever the kettle is in an upright position or during the time when the nozzles are covered or partially covered with molten metal, gas must be continuously introduced into the furnace. The gas pressure and the flow rate must be measured in such a way that a Flow of molten material through the nozzles or clogging of the nozzles is avoided

The addition of scrap to the furnace can be done in a single batch at the beginning or in a few batches during the heat treatment. This depends on the bulkiness the scrap from · The higher the bulkiness of the used The less thrusts that can be made · With light scrap, more than one thrust is necessary · When the ratio of molten steel from the previous smelting to the new batch of scrap is high, then can the scrap can be brought in in one or two batches. If the ratio of the remainder of the melt to the new scrap is low, then this will, on the other hand, result in higher hetto production of new steel per melt. However, the scrap material must be added in several batches. The scrap material is advantageously far into the molten steel sunk and advantageously the continuous phase in the bath is always molten steel or iron

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Not all reactions that occur within or below the surface of the melt are known. the The types of reactions that occur will vary and depend on a myriad of factors, including, the type the oxidant used, the specific fuel used, the oxidant to fuel ratio used, the admixture content and the contamination of the ferrous metal that becomes hairy, the type and amount of materials which can be added to the melt during the process, the process: driving conditions, the properties of the desired end product, etc. One of the reactions that occur when using relatively pure oxygen and methane as the Fuel take place are described below

At the beginning of the flow of the gaseous fuel, at Using natural gas, the overall effect besides the fire-resistant lining in the area of the hydrocarbon fuel additive is endothermic, i.e. when hydrocarbon, especially methane, is used the melt becomes cooled by the noticeable heat requirement and the endothermic cracking reaction (1)

OH ₄ - »0 + 2H ₂ (1)

However, the introduction of oxygen should be carried out as soon as possible started to take advantage of the overall exothermic reaction of oxygen with the fuel. There If the melting point of scrap is near 1 · 510 ° Ο (2,750 ° F), the chair must operate at relatively high temperatures, i.e. in the range of 1,600 to 1 · 650 ° Ο (2,900 to 3,000 ° F).

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The heat development is the result of the reaction of the oxygen with iron, its oxidizable additions, such as C, S, Mn, etc., and fuel gases, such as hydrocarbons and carbon monoxide

To get the required heat in the bath, it is desirable «in the weld pool with a relatively high oxygen level to work, which is consistent with a low carbon level · This promotes the combustion of Hydrogen. On the other hand, when working in the melt with a high carbon level, »the environment more reducing, and the hydrogen and carbon monoxide that rise from the fusion become less "Even if the carbon level in the molten steel is high" oxidizes "a considerable amount of iron oxide becomes (FeO) in the refining slag layer. This means that the hydrogen and the carbon monoxide are going through rise up the bath, become oxidized as a result of a reaction of the FeO in the slag according to equation (2)

FeO + H ₂ grr »Fe + HgO (2)

At this temperature it is approximately 1,650 ° C (3,000 ° F) the reaction is weakly endothermic. The same applies to the reaction (3) between carbon monoxide and iron oxide

FeO + CO ^ = £ Fe

However, the total reaction includes the union of carbon with oxygen and the summation of the oxidation of iron and its impurities included therein the decomposition and reduction reactions (1) ». (2), and (3) o The overall reaction is exothermic.

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Because the endothermic reaction (1) is a cooling of the nozzles caused on the ground and therefore the problem of possible nozzle clogging exists, it is advantageous «a mixture of oxygen (from an auxiliary source such as 82 in Figure 2) and hydrocarbons such as methane and oxygen Introduce such a mixture through fuel line 26 below the surface of the melt 30 should of course contain an amount of oxygen that is below the self-immolation limits of the mixture the existing temperatures and the pressure are «vie Mentioned previously, the introduction of oxygen should be above the Melt surface are started as soon as possible, in a similar way as that in the known basic oxygen process. As with the basic oxygen process, heat is generated, but the similarity ceases because in this process hydrocarbon fuel, in particular Natural gas is oxidized to CO, COp and water vapor, according to the following overall reaction (4).

CH _n + 0.5 (i + x + y) 0 ₂ - ^ yH ₂ O + (^ y) H ₂ + (1-acCO + xC0 ₂ (4)

The y moles of water vapor and the χ moles of carbon dioxide that fc at thermodynamic equilibrium with the resolved Oxygen can be formed in the steel melt in the usual way by the free energies of the reaction can be determined at the temperatures of the melt. The following apply to the oxides of carbon and hydrogen Relationships and equilibrium constants before:

9098S 1/1 1 1 β

POO ₀ Z /

OO + O- »GO ₂ ; Z ₁ - ^g » ³ ^ (5a)

(a _o ) (POX)) Ca ₀ ) (1-

y / ir

(a _o ) (PH ₂ ) (a _o ) (1-

You can see that the total pressure ₉ T _{t has} no influence on the ratio of 0O ₂ to 00 or of ILjO to H ₂ .

They generated heat from the overall exothermic reactions serves to melt the scrap through heat transfer due to liquid convection from the molten steel on the solid scrap

In steelmaking, temperatures in the range of 1,600 ° C to 1,700 ° 0 (2,900 ° F to 3,100 ° F) require the COg / OO ratio to be low in order to satisfy the equilibrium of reactions (5a) and (5b). On the other hand, the opposite is the case at these temperatures with regard to the ratio of HgO / Hg, which is relatively high, ie 0.75 · This means that a considerable amount (40 to 45%) of the vase cloth from the heat (1) is oxidized with considerable heat emission · This' agrees with the method according to Ολχ invention: üevein.

The procedure is under subsequent additions of Scrap continued · Every time scrap is added the oxygen lance is £ 4- (or the bilge 54- and 35) is raised and the scrap charge is added, the fuel being continuously introduced through the nozzles 23

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will * The refining of the molten scrap leads at the same time to the oxidation of such impurities or alloying components in scrap such as silicon " Manganese, vanadium, niobium, zinc, titanium, aluminum etc.

The method according to the invention can work with practically any carbon content, but it is advantageously worked with a content below approximately 1 % carbon, since a low carbon content promotes the oxidation of the above-mentioned admixtures as well as the oxidation of the hydrogen from the fuel supplied. The higher the oxygen content of the steel (and therefore the lower the carbon content), the greater the utilization (oxidation) of the hydrogen and the release of heat and the lower the hydrogen content of the steel when the melting is complete. The carbon content of the melt can of course be controlled to some extent by adjusting the ratio of oxygen to fuel. If the ratio of fuel to oxygen increases, then the carbon content of the melt also increases and vice versa.The carbon content can also be increased by blowing fine, solid carbon or carbon-containing solid matter in suspension in the hydrocarbon fuel, or by injecting hydrocarbon fuel. Fuels with a relatively high C / H ratio are used · If the fuel composition and oxygen supply are set correctly, some of the carbon can be supplied directly from the fuel according to equation (1).

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Whenever the scrap lances are removed, the oxygen level tends to decrease and the carbon content to increase. In general, however, preferred to work with low carbon content in the melt, "ie, near the oxygen" saturation, as this is a more complete oxidation DEE hydrogen asks "From can & ühtungen simple GleichgewichtsTbete a general Gleiotasg (6) gesctaiebegi to give wa used methane as fuel & "Sisiö assumes a melt saturated with oxygen (generally with the reduction of JeO to Fe)""

These conditions promote the comprehensive O ^ dation of the Hydrogen in the stahibado However, it is necessary aie & fc j that the bath is completely saturated with oxygen or near the Lang © vorfibesfahren not la. ©! © ieJhgewicht Lying conditions prevail, - where the amount of hydrogen is much higher and where the 0xydati®a of hydrogen and Köhl © nmonO3grd is carried out to the extent indicated by reaction (6), even if the average oxygen content lsi in the melt does not reach saturation, it is therefore preferred mirror at low carbon (below 10 points) to work with setting the carbon it to the desired level when reaching the desired heat «if a higher carbon content due to the demands on the melt is required, carbon content can be increased slightly by increasing the fuel / oxygen ratio be by getting solid carbon or higher Introduces hydrocarbon fuels that are suspended in the fuel gas, or by subsequent

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Topping up · If a damming up of the carbon is desired, at the end of the heating it is possible to stop the oxygen supply while the blowing in of the; Continues fuel "additive so the carbon to promote · piping latter practice tends, however, to cool the melt · A way" lower this AbkÜhlungseff ekfc ι be blown to the surface of the boiler during aer fuel supply oxygen to the exhaust carbon monoxide to carbon dioxide and to oxidize hydrogen to water vapor, reactions that give radiant heat to the bath. Another way to reduce the AbMihlungseff ect is to inject solid carbon which is suspended in the below the melt blown gaseous fuel "This reduces the cooling effect per dot carbon addition _$ because of the endothermic profile of the AufIffsungsreaktion for fixed carbon is far less than the EndoTherm® Cracking reaction for hydrocarbons, especially methane «

In case of decarburization at the end of melting with hydrocarbon fuel is dissolved hydrogen on the steel given what is not desirable, especially not at P whole or semi-calm steel «hydrogen can be produced by vacuum degassing removed, but this includes a second pass * Hydrogen can also be quite easily be degraded by nozzle degassing »which is usually with the bubbling of a noble gas through the molten one Steel is connected »The preferred method for the invention Method of removing hydrogen is by introducing carbon dioxide into the nozzles on the bottom, at the very end of the melting process, just before the pouring out. “Carbon dioxide goes with hydrogen as follows ! Reaction one

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CO ₂ + 2 | h | ? OO + H ₂ O (7)

The hydrogen removal is very rapid because the formed Köhlesiaenosard tends to take hydrogen with it, as is the case with nozzle degassing

Finally, it will usually be desirable to have some control over the sulfur content of the resulting Wielding steels · This is done without difficulty by adding the sulfur introduced into the fuel keeps to a minimum. It is relatively easy to use any gaseous hydrocarbon fuel desulfurize · This is in direct blessing to the Difficulties «occurring in the desulfurization of coal, coke and liquid fuels« ·. "

Figures 3 and 4 show an embodiment of the invention, in which both the fuel and the oxygen are introduced below the melt 30 of the furnace The same numbers in this figure relate to the same items as in Figures 1 and 2 · Ub is to be able to introduce both reaction components below the melt it is advisable to «convert the bottom part of the stove a little · The bottom 100 in FIG. 3 therefore delimits an antechamber for the fuel and a chamber 102 for gases containing oxygen. The chambers are surrounded by a suitable partition divided · A fuel line 105 provides the desired Connection between the fuel source (not shown) and the fuel pre-chamber 101 · An oxygen line 106 provides for the desired connection between the oxygen source (not shown) and the oxygen pre-chamber 102. Because at the Outlet opening of those nozzles from which oxygen is introduced into the melt is introduced, intense heat can be generated, it can

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be necessary to use a diluent with the oxygen to mix. The line 107 is provided for this, which is connected to the oxygen line 106 and for guidance a suitable diluent is established · The diluent can either be a noble gas or it may be largely oxidized exhaust gases from line 66 (Figure 2). Check the temperature at the outlet opening of the Nozzles are necessary to prevent excessive wear and tear on the heat-resistant material in this area · The Furnace according to Figure 3 has a gas discharge line 111

In the course of operation of the furnace of Figure 3, the chemical processes are essentially the same as in Figure 3 above individual described for the method of operation according to Figure 2 · The only difference is that swohl the fuel and the oxygen below the bottom of the Melt 30 are introduced

The furnace embodiment according to FIGS. 5 and 6 represents a modification of the device and the method. In this modification, both the oxygen-containing Gases as well as the fuel, either liquid or gaseous, are introduced at the surface of the melt through lances · These Drains can either be arranged above the melt or in this be immersed. Unless it is necessary to provide nozzles for introducing one or more of the gaseous components in the bottom part of the furnace, the furnace can be a take on more or less conventional "cup-shaped" shapes as shown in Figure 5. As can be seen, it is from a heavy outer structure 115 is formed, which is lined with old fire-resistant material 116. Vie becomes common he of journal 11? held, in turn by supports 118 and 119, which are on a suitable foundation 120

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are attached «rotated and held». The furnace is provided with a cover part 122, which is covered with fire-resistant Material 123 is lined · Within the volume 125 are three separate zones or sections 126, 127t and 128 demarcated · It may be desirable * the internal volume of the furnace largely above the melt partially to divide into sections} to isolate the components «which are introduced into the melt. This can be convenient done by a three-armed partition wall 130 (Figure 6), which is protected by a ceramic coating 135 is · Oxygen is introduced through an oxygen lance 137t which protrudes into section 127, and becomes fuel introduced through a lance 138 protruding into section 126 Finally, the third section 128 is set up to receive the scrap continuously or in batches. "This is preferably done by using a scrap hopper 140, which is connected to section 128 of the furnace by a appropriate inlet 141 communicates

Although the method according to the invention in particular it is directed that the reaction of a fuel and an oxidizing agent takes place below the surface of the melt, It is not necessary that all fuel and oxidants React in the Molten Cash Register · A smaller amount of heat can be caused by the reaction above the surface of the melt and is mainly supplied to the melt by radiation.

The most advantageous reduction fuels that can be used to practice the invention are natural gas and reformed natural gasesNatural gas, which consists primarily of methane, is advantageous because of its heat resistance,

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the ease can be desulfurized with it, its relatively high hydrogen to carbon ratio and the ease with which it can be handled © reformed natural gas or steam reformed natural gas, the typiecherweise about 74% hydrogen, 16% CO, 6% GK) _{Contains 2} and 4 % CH ^, has similar door parts as the natural gas mentioned above to enable the invention to be carried out

The use of recirculated furnace gases or exhaust gases generated in the method according to the invention can Likewise, if recirculated exhaust gases are used, it is generally advisable to do so before Recirculation to condense any water it may contain, and perhaps the washing out of it if necessary existing COg, provided this is under the process conditions used is desirable

Some amount of solid fuel, such as carbon, Carbide, ferro-silicon, etc., can be used during the Baffinierungsverfahren also added directly to the bathroom if this is considered desirable or advantageous

The oxidizing agent used according to the invention is advantageously very pure oxygen and is either as high pressure gas or as a liquid, which then is evaporated by suitable known means, draw / leads * However, the oxygen does not need pure

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substance, but can contain certain diluents »as long as the oxygen contained is sufficient} to to be able to carry out the invention and the diluents the course of operation of the method according to the invention or do not adversely affect the steel obtained · For example, the oxygen source may not only contain pure oxygen "but also relatively pure oxygen" like oxygenated air and carbon dioxide · The The amount of air used should be kept so low that its nitrogen content reaches the desired nitrogen content of the steel obtained is not adversely affected

The ratio of oxidant to fuel is chosen depending on the type of oxidant and fuel used, as well as the content of impurities in the treated ferrous metal in solid fuel "the type and amount of materials" added to the melt during the process Can "etc. If the metal to be treated contains, for example, about 3/4% carbon" not as much fuel needs to be used as "if the metal to be treated contains only 0.5% carbon" The ratio of fuel to oxygen should preferably be set in this way ensure that a neutral or reducing environment is maintained within the melt.

When there is excess oxygen, iron oxide becomes Although this is not particularly unpleasant, it requires an increase in fuel or a decrease in oxygen in order to reduce the iron oxide. The problems associated with using an excess of fuel vary depending on the type of fuel used Fuel different · An excess of methane, for

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Example that causes an endothermic reaction can be a Cause clogging of the nozzles, a decrease in the melting temperature or simply a loss of fuel, since it is not consumed during the reaction and combines with the exhaust gases

When using natural gas or methane as the fuel, it is beneficial to have a molar ratio of hydrocarbon too Maintain oxygen at approximately 1: 1 · The exact proportions of natural gas or other fuels too Oxygen depend on the fuel used and others factors mentioned above and can be determined by routine tests and calculations

If the metal contains a significant amount of impurities that act as fuel and when reacting with one. Oxidizing agents generate heat, these are burned off during the process, and it may be necessary or desirable at a later stage in the metal production increase the amount of fuel to a neutral or to maintain a reducing environment and thereby a to prevent inadequate burning of iron

The method according to the invention has been described above using essentially all types of steel scrap or Iron scrap described for which it is most beneficial, but are the ferrous metals or the Scrap steel that can be used in accordance with this invention, those ferrous metals or mixtures thereof that do not contain sufficient fuel additives, such as carbon, silicone, Manganese, etc., contained in order to generate the necessary heat for conversion

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or refining the ferrous metal into a usable one To produce steel product using oxygen alone.This would be, for example, conventional blast furnace pig iron not covered by these terms, as it contains enough solid fuel additions to be in the basic Oxygen process to react with the oxygen, and therefore the use of additional fuel would not be necessary or required. she Close the "ferrous metal" and "scrap steel" provisions however, both iron and steel from known scrap sources, like old cars, accrued in a known manner in the factory Scrap, as well as mixtures of pig iron and ferrous metal, such as scrap steel with a common solid Fuel admixture content which is so low that the necessary heat cannot be obtained by introducing oxygen alone are generated by the basic oxygen process can.

Her invention also attracts the addition of various known refining chemicals such as calcium oxide, ferrosilicon and the like, to the melt into consideration · This can be done by using such materials together with introduced into the scrap or by suspending them either in the oxygen stream or in the fuel stream will·

It can thus be seen that the invention is a method and a device for converting scrap metal into usable steel without the disadvantages mentioned the earlier devices and methods provides · As the reactants (oxygen and fuel) in almost each area are present, the application of the method is not limited to a few specific areas, so as is the case with the arc process · Finally

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makes it possible to control the chemical composition of the reactants «the composition control of the steel.

The oxidant or relatively pure oxygen will dissolved or absorbed when it is introduced into the melt »essentially saturates the melt pool with Oxygen, allows the exothermic reactions to take place beneath the surface of the melt and causes the heat of reaction to be released beneath the surface of the melt. Ee is believed to be the subsurface of the melt the reaction going on is a circulation or a fairly causes strong movement within the melt and is fairly evenly distributed in the melt, making it hot Places to be avoided

They shown in the drawings melt pools 30 and the Slag layers 32 are shown in a quiescent state · The slag layer is likely due to movement mixed with the molten metal bath during the process · Whether the entire bath is in motion during the process and the slag layer is mixed with it is not known

Both the amount and the pressure of oxygen addition can according to the invention on a fairly broad basis be varied "which depends on a ^ y.n'hi on factors, such as the type of container used, the The amount and type of ferrous metal batch to be treated, etc. Of course, the amount of oxygen must be related to the reducing fuel introduced into the molten bath, as described above. The rate of oxygen addition can also be varied, but it should be kept so that a perfect one

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Dissolution of the oxygen in the weld pool guaranteed is "so that the desired ratio between the oxygen and the reducing fuel can take place inside or below the surface of the molten bath

The oxygen pressure can be between approx. 3 »5 and 10 kg / cm (50 and 150 pounds) lie “but the invention is not limited to this specific pressure range · Typically, the oxygen cannot consume enough energy Transfer of the molten bath in order to induce a stirring or a circulation movement of its own accord · The inside the The exothermic reaction taking place in the bath can also cause the molten bath to move due to thermal currents Doubt caused by the gas blown through the melt · The exothermic reaction also has the advantage «the Melting temperature can be maintained more time for the addition of various additives "such as carbon" to allow "to form the desired steel" and in order to prevent iron oxidation «even if the molten bath contains a very low carbon or admixture content ·

The lances and nozzles which can be used according to the invention can can be designed in a simple manner by those skilled in the art, for example with regard to the opening widths the type of batches to be treated, the velocities and volumes of gases required or desired for the individual batch, etc.

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Example ,

180 kg (400 pounds) of cold scrap steel containing approximately 0.2% carbon * was placed in a furnace which had an inside diameter of 0.4 m (16 inches) and a maximum capacity of approximately 450 kg (1,000 pounds) , introduced "The furnace was equipped with coils for induction heating in a conventional manner, and the cold scrap was melted by induction heating"

Commercially available natural gas was then added to the melt through four nozzles, 6.35 mm (1/4 inch) in diameter, connected to the bottom wall of the furnace as shown in Figure 1 shown were connected »The gaseous oxygen was simultaneously onto the surface of the molten steel through a single diameter lance of conventional design 1/4 inch (6.35 mm).

The inflow rates of the natural gas and the building material were Maintained essentially the same, it was run at approximately 17 standard cubic meters per hour (10 standard cubic feet per minute) and then increased continuously up to about 60 normal cubic meters per hour (35 standard cubic feet per minute). The flow rate of oxygen was increased by increasing the dynamic pressure from about 3.5 to 9 kg / cm (50 to 130 pounds) was increased.

Since the inflow of both oxygen and As natural gas was increased, less heat was required from the induction coils. After reaching the higher flow rates, there was a reaction between the oxygen and the natural gas both sufficient to keep the steel in a molten state and largely the heat losses that

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were relatively high for the small container used. »The oxygen and natural gas supplies were stopped, the container tilted, and approximately 4-5 kg (100 pounds) of the molten steel was dumped into molds with no addition of carbon or other additives ; » The steel obtained contained approximately 0.01 % carbon. The carbon content of the steel obtained can of course be varied to the desired degree as described by blowing carbon into the bath through a steel pipe or by adding it to a pan or by other conventional means.

The container was then placed in an upright position and approximately 9 kg (20 pounds) of additional steel scrap containing approximately 0.2% carbon was added, the top of the container re-closed, and the introduction of the natural gas and oxygen restarted xma continued until the additional batch was melted "

The process of heating, pouring, and filling a of additional scrap as described above can continue a

Various modifications of the method and the device can of course be done without departing from the scope of the invention.

For example, as already stated, the nozzles 23 in FIG. 1 can be closed off or omitted and either one of the lances 3 ^ or 35 lowered into the bath in order to allow the exothermic reactions to take place essentially completely below the surface of the bath. "

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Claims (1)

A 12 13V35 P a t e η t a ns ρ r Ü c h e 1 · Process for converting ferrous metal into steel, characterized in that an oxidizing agent with a fuel largely below the surface of a melt of ferrous metal, in the scrap steel is immersed, is implemented 2 · The method according to claim 1, characterized in that essentially the entire reaction between the oxidizing agent and the fuel takes place below the surface of the melt 3β method according to claim 1 or 2, characterized in that that the fuel is a gaseous hydrocarbon is used, 4 · «Method according to claim 3, characterized in that that the hydrocarbon fuel consists primarily of methane 5. The method according to claim 2, characterized in that reformed natural gas rich in hydrogen is used as fuel is used· 6 · Method for converting ferrous metal into steel, in particular according to one of the preceding claims 1 to 5§ characterized in that one is in a molten bath additional ferrous metal obtained from ferrous metal from a suitable source and such amount of 909881/1116 A 12 134/35 Introduces oxidizing agents and reducing fuel, that an exothermic reaction takes place essentially completely below the surface of the molten bath and releases a sufficient chemical enthalpy of reaction to melt the iron metal introduced 7. Yerfahren according to any one of the preceding claims, in particular according to claim 6, characterized in that the ratio of the oxidizing agent to reducing agent Fuel is maintained so that a substantially neutral environment for the oxidation or reduction of the Stahls is maintained. 8 · Method according to one of claims 1 to 6, in particular according to claim 6, characterized in that the ratio of oxidizing agent to reducing fuel so it is held that a reducing environment results, 9 »Method according to one of claims 6 to 8, characterized in that that the source of the ferrous metal supplied is at least partly, in particular predominantly, Is scrap steel. 10 «Method according to one of the preceding claims, characterized characterized in that the oxidizing agent is essentially pure oxygen gas and that of is introduced into the melt pool above the melt surface, and that the reducing fuel introduced below the surface of the molten bath will. 909881/1116 A 12 134/35 β method according to any one of claims 1 to 9 t thereby characterized in that relatively pure oxygen is used as the oxidizing agent, and that the oxygen and the reducing fuel is introduced into the melt pool from above the melt surface will. . 12. The method according to any one of claims 1 to 10, characterized in that the oxidizing agent is relatively pure Oxygen is used and that at least a portion of the oxygen and the reducing fuel be introduced below the surface of the weld pool. 13 * Method according to one of the preceding claims, characterized characterized in that following the reaction step for setting the final composition of the steel at least one additive is introduced into the weld pool «, 14, method according to claim 13, characterized in, that carbon is used as an additive. 15 · Process for converting scrap steel into steel, in particular according to one of the preceding claims, characterized in that an input material, which consists mainly of scrap steel, is introduced into a molten bath made of steel, gaseous oxygen reacted from an oxygen source and reducing fuel below the surface of the molten bath and thereby generate heat and create a neutral environment and that the mainly hydrogen, Carbon monoxide and water vapor are extracted from existing exhaust gases, _ 909881/1116 A 12 134/35 16 · Method according to one of the preceding claims, in particular according to claim 15ι characterized in that the oxygen is at least partly in the form of air » 17o method according to claim 15 or 16, characterized in that that the exhaust gases are burned to produce heat for preheating at least one of those introduced into the system To create components 18 · The method according to claim 17 «characterized in that the preheated component is the scrap and the burning of the exhaust gases in such a series of operations it is carried out that the scrap is exposed to combustion gases which are inherently reducing and the temperature increases during preheating 19. The method according to claim 17 or 18, characterized in that that the oxygen source is preheated 20 · Method according to one of Claims 17 to 19 »thereby indicated that the fuel is preheated Method according to one of the preceding claims, characterized in that at least one (part of the Oxygen is mixed with fuel before it is introduced into the weld pool. 22ο Method according to one of claims 15 to 21, characterized characterized in that at least some of the exhaust gases are returned to the weld pool 909881/1118 A. 12134/35 23 Device for converting scrap steel into shape * steel, in particular for carrying out the method according to one of the preceding claims by one lined with a refractory material Container for holding a ferrous metal melt, a feed device to add ferrous metal to load this container, a feeder for introducing a reducing fuel under the Surface of the weld pool, a feed device for introducing an oxygen source into the weld pool, wherein the feed means for the fuel and the oxygen are arranged so that between the fuel and the oxygen react within of the molten pool is effected, as well as means for withdrawing resulting exhaust gases from the Container. 24 · The apparatus of claim 23t wherein the container has a bulged shape and tilted 1st and that is formed by the bulge, a volume for containing molten and solid metal without this in contact with the feed means for the fuel and / or the oxygen comes 25 · Device according to claim 23 or 24, characterized in that that the container is designed as a pressure vessel. 26β device according to one of claims 23 to 251 characterized characterized in that the container has a plurality of injection nozzles, which in the upright position of the container are below the surface of the melt, 909881/1 1 16 A 12 13V35 27 · Device according to claim 26, characterized in that that the injection nozzles for the feed device for the fuel and possibly also for the oxygen belong· 28 «Device according to claim 26, characterized in that that the feed devices for the fuel and the Feed oxygen separately from each other under the weld pool into the container 29 «Device according to one of claims 23 to 27, characterized characterized in that the supply device for the oxygen has at least one lance for directing the oxygen source onto the surface of the molten bath. 30. Device according to one of claims 23 to 25, characterized characterized in that the supply devices for the oxygen and the fuel have separate lances for injecting the oxygen source and the fuel from the surface in the weld pool. 31 · Device according to one of Claims 23 to 30, characterized by a device for combustion an additional amount of oxygen and fuel over the surface of the molten pool. 32. Device according to one of claims 23 to 31 «characterized by at least one device for Burning exhaust gases 9 0 9 8 8 1/1116 A 12 134/35 33 · Device according to claim 32, characterized in that that the device for separating the exhaust gases a number of. Has combustion chambers through which the Metal is passed before its introduction into the container and these combustion chambers relative to the feed device of the ferrous metal are arranged so that the ferrous metal with progressive preheating Exposed to combustion gases with increasing reducing properties, in particular countered, is β 90988 1/1116 Empty barrels