LU87759A1 - PROCESS FOR THE DIRECT MANUFACTURE OF STEEL AND OTHER FOUNDRY PRODUCTS - Google Patents

Description

PROCESS FOR THE DIRECT MANUFACTURE OF STEEL AND OTHER FOUNDRY PRODUCTS DESCRIPTION

OBJECT OF THE INVENTION

The present invention relates to a process for the direct manufacture of steel and other foundry products, starting from materials which contain metals and which have a relatively large surface area, such as for example fine-grained materials or shavings coming from works of turning or grinding which are mixed with used or residual oils, or with other mixable energy carriers or which are already mixed with them, such as for example the oils normally used for the machining of these materials, etc. BACKGROUND OF THE INVENTION.

Currently, the manufacture of steel is carried out by indirect processes, which are divided into two phases, the first consisting in obtaining liquid iron oxide which is then introduced into converters where it is added to the iron crude liquid and oxidation is carried out and in which this crude iron with a high carbon content and other prejudicial products is subjected to decarburization and to regulation of the content of sulfur, phosphorus, silica, magnesium, etc. The liquid iron oxide is at the same time rid of oxygen.

Among the oxidation or decarburization methods, particular mention should be made of the endless Bessemer and Thomas processes, in which molten iron is injected into a stream of air which burns the impurities in the cast iron.

There is another method consisting in injecting oxygen and which makes it possible to avoid the prejudicial action of the nitrogen contained in the air, thus ensuring the obtaining of a product of better quality.

Finally, and although there are many other processes, we will particularly mention the LD process (LINZ-DONAWITZ) based on the oxygen blowing by means of a lance, as well as on the addition of lime on the surface of the bath.

All these processes currently used, as indicated in the foregoing, are methods of indirectly obtaining steel, since the molten iron must be transferred to the converters for its decarburization and therefore this process is divided into several phases, with the technical problems this entails.

The current process for obtaining steel by reduction in blast furnaces leads to an intermediate product, called "raw iron" because the reduction of oxygen in the iron ore inevitably gives rise to the carburation of iron, which which requires a subsequent oxidation operation to release the carbon from the iron and the other harmful elements which accompany it. On the other hand, the processes usually used today for the manufacture of steel require intermediate storage in landfills, enormous quantities of residual materials from manufacturing, which gives rise to a clear contamination of the environment.

Finally, it should be added that the known tests carried out worldwide to avoid these residual materials only lead to the solution which consists in destroying them in combustion plants, which obviously implies the formation of new storage or storage locations. discharge of solid residual materials, pending their combustion, which again leads to contamination of the environment.

DESCRIPTION OF THE INVENTION

Thanks to the present invention, steel is obtained by a direct method by making not only that the residual materials are liquefied, but also by carrying out a supply of oily ferric oxides (finely divided iron mimerai), which makes it possible to produce the direct manufacture of steel starting from ferric oxides, so that this fusion of ferric oxide involves its direct transformation into steel. The expression "direct manufacture of steel" means that the ferric oxides are rid of oxygen by reduction operations, and are transformed directly into steel without it being necessary to obtain intermediate products.

In the direct manufacturing process according to the invention, the oxygen of the ferric oxide reacts immediately with the carbon of the raw iron or liquid iron in the converter, due to the fact that the ferric oxide in question is added under liquid form, so that the reduction is almost immediate, the oxygen of the ferric oxide combining with the carbon of the liquid iron, which gives rise to the immediate manufacture of the steel, without generation of any intermediate product .

This reaction takes place endothermically, i.e. it absorbs energy, consuming part of the heat of the process, which can be offset by an increase in the content of silica in the liquid crude iron. , if one wishes to obtain a steel of more or less good quality, or by means of the addition of a lesser amount of cooling scrap, or even by means of the LD converter process (LINZ-DONAWITZ).

The process according to the invention in which the operation is carried out continuously is carried out as follows:

First of all, the ferric oxides are prepared, by the use of shavings from turning, grinding, etc., which are impregnated with the cutting oil used during the machining. Non-oily ferric oxides can also be used to which used oils or residual oils are added or with which they are mixed as an energy supply or support for the mixing process with liquid iron, thus ensuring the carrying out of the process in continuous regime.

Then, these ferric oxides which contain oil or to which waste oils or residual oils have been added are subjected to preheating at approximately 400 ° C. or at slightly higher temperatures, by heating them indirectly in a shaft furnace. well known, these ferric oxides being introduced into the combustion zone by means of one or more devices in the form of furnace supply tubes, the penetration of the oxides into the furnace taking place from the upper part to the part lower.

The oily liquids adhered to the residual materials give rise to the formation of a pressure to which the mixture of vapor and gas is subjected, which is used in the supply devices to exert a pressure directed downwards on the combustion zone of the materials introduced, that is to say on the residual materials mentioned above, since the feed devices are closed upwards and outwards, in the usual way well known for feeding the tops stoves.

Indirect preheating is adjustable by means of feed adjustment devices, so as to obtain, on the one hand, a sufficient pressure of the mixture of steam and gas and, on the other hand, that there is still enough elements for supporting or providing energy for the treatment, on the surfaces of the combustion materials in the combustion zone of the shaft furnace, so that the residual materials mix quickly with the molten metal

The main advantages obtained with the process according to the invention would be the following:

All energy carriers for processing, such as, for example, oils added to ferric oxides, which may be used or residual oils, as well as oils from machining or the like, generally energy carriers, are burned optimally at a temperature above 1,500 ° C which is a temperature close to that of steel melting (1,600 ° C), this combustion taking place on relatively large surfaces. These oils or these energy carriers are destroyed more securely than in the usual way, with, if necessary, the possibility of blowing oxygen to activate combustion.

A second advantage to be highlighted consists in that the chamber furnace chamber into which the feed device penetrates until it reaches the lower combustion zone of the comb furnace, surrounds this device by means of an furnace chamber free, relatively high and of large volume as a whole, which thus allows an optimal and safe superior combustion to be obtained by means of a supply of secondary air or pure oxygen.

This possibility especially has the advantage of allowing used or residual oils (containing PBC) to be destroyed with greater safety than with traditional methods.

Thirdly, and by means of spontaneous and intensive combustion, ensured by the large combustion surfaces, a rapid transformation of the residual materials is obtained, which mix with the molten metal, so that the oxidation is maintained at a very low level, which is especially important when using chips from turning or other machining jobs.

Fourth, in the hearth of the shaft furnace where the foundry products are received, steel can be manufactured directly, by means of a metallurgical reduction treatment starting with molten ferric oxide, with the possibility of also using other elements in addition to raw iron or liquid iron.

The process described allows, for the first time, the direct manufacture of steel, continuously, starting from ferric oxide, which could not have been obtained before with any other process, this transformation of ferric oxide. which can be carried out, on the one hand in the furnace hearth and, on the other hand, by the method mentioned above of manufacturing steel in a converter.

Of course various modifications can be made by those skilled in the art to the devices or methods which have just been described solely by way of non-limiting example without departing from the scope of the invention.

Claims (12)

1. - direct steel manufacturing process and other foundry products using relatively large area metallic materials, such as example of fine-grained materials or chips from machining, which are mixed with used oils and residual or other elements carrying energy or which are already mixed with these materials in a shaft furnace provided with a tube-shaped feed installation, characterized in that these fine-grained materials or these chips are indirectly preheated from the top of the shaft furnace through the plant tube-shaped feed to the combustion zone of the shaft furnace, which is in its part lower, so that these products thus heated are transferred to the fluid cast iron or liquid iron by means of an intensive and spontaneous combustion of the energy carriers which adhere to them or which are in the form of vapor or gas, which can be subjected continuous metallurgical treatment in the hearth of the shaft furnace or in other similar installations, which makes it possible to carry out the direct manufacture of steel or other metal foundry products. 2. - Method according to claim 1, characterized in that, to the above materials of metallic content as well as to materials without oil content, such as iron oxides and other metallic materials, used or residual oils are added, and materials containing oil and other mixable energy carriers are used to act as process energy carriers. 3. - Method according to claims 1 and 2, characterized in that materials producing steam or gas are added to all materials of metal content with relatively large surfaces. 4. - Method according to claims 1 to 3, characterized in that one adds, in addition, oxygen in the combustion zone of the shaft furnace. 5. - Method according to Claims 1 to 4, characterized in that secondary air and oxygen are added to the combustion zone 6. - Method according to Claims 1 to 5, characterized in that additional used or recycled oils, containing PCB, as energy-carrying elements for treatment. 7. - Method according to claims 1 to 6, characterized in that the metallic content materials are transferred into the hearth of the tank furnace with fluid cast iron 8. - Method according to claims 1 to 7, characterized in that in the hearth of the shaft furnace, all the fluid cast iron products are metallurgically treated. 9. - Method according to claims 1 to 9, characterized in that the fluid molten products are then subjected continuously to a metallurgical treatment by means of other well-known treatment methods. 10. - Method according to claims 1 to 9, characterized in that, in the steel conversion process, the liquid iron oxide is added to the liquid crude iron. 11 · - Method according to claims 1 to 10, characterized in that, during the process of conversion to steel by reduction of crude iron or other energy carriers, the liquid iron oxide is transformed directly into steel. 12.- Method according to claims 1 to 11, characterized in that the liquid iron oxide located in the hearth of the shaft furnace, on raw iron or other reducing carriers, is transformed directly into steel.