MXPA00000108A - Method for using coal fines in a melt-down gasifier - Google Patents

Abstract

The invention relates to a method for producing liquid metal, in particular liquid pig iron (9) or liquid steel intermediates from metalliferous elements, in particular from partially or totally reduced sponge iron (3) in a melt-down gasifier (1). Carbon-containing material, consisting at least partially of coal fines (16) and coal dust (13), is fed with oxygen or an oxygen-containing gas to a bed (4) formed of said carbon-containing material. The metalliferous elements are melted down, forming a reduction gas, optionally after preliminary final reduction. After drying, the coal fines (16) and coal dust (13) that are to be used are mixed in the warm state with bitumen (20) and then briquetted in the cold state. The briquettes (25) thus produced are introduced to the melt-down gasifier (1) in the cold state and subjected to shock heating (1).

Description

METHOD FOR USING FINE CARBON IN A FOUNDER GASIFICATOR DESCRIPTION OF THE INVENTION: The invention relates to a method for the production of liquid metal, in particular pig iron or liquid steel pre-products, from metallic carriers, in particular reduced or partially reduced cancellous iron, in a gasifier melter, where with the supply of carbon-containing material at least partially formed of coal, fine and coal dust and oxygen supply or an oxygen-containing gas the metallic carriers melt in a bed of the carbon-containing material with the simultaneous formation of a reducing gas optionally for a previous final reduction, and a plant to carry out the method. A problem that arises in the loading of the material containing carbon in fine particles, such as fine coal and coal dust, to a melting gasifier, is that the material containing carbon in fine particles due to the gas velocities that exist in the gasifier smelter, is immediately taken out of it again. This also applies to fine-grained ore to some degree. To prevent this, it has been proposed in AT-B-401 777 to load carbon carriers to the melting gasifier together with fine ore and / or mineral powder by means of REF .: 32265 of dust burners, properly to the lower region of the smelter gasifier. With this process, the substoichiometric combustion of the charged carbon carrier takes place. A disadvantage of this is that the carbon carrier can not contribute to the formation of a bed formed of solid carbon carriers in the melting gasifier. It is internationally known to charge carbon in fine particles to a coal gasifier in the upper region thereof, where the fine particle carbon is reacted to coke, the coke is carried out together with the reducing gas and separated and together with the fine particle material is subsequently supplied to a melting gasifier through a burner. However, this does not contribute to the formation of a bed of carbon-containing material. This bed is usually formed of bituminous coal of more than 10 centimeters, which must have a high thermal stability. Due to the development of the coal market, which is governed by the demands of the operators of the coal-fired power stations, the situation can arise that fine coal is preferentially offered for the coal dust burners that are customary at present. Fired grills that were previously the practice and that needed the bituminous coal load, now play a secondary role in the coal consumer market. As a result, the fine portion of the carbons offered in the market can assume considerable proportions, reaching up to 50 or 70%. When loading such coals into a melting gasifier, the fine coals usually must be sifted first so that the coarse fraction, that is bituminous coal, is available to charge the melting gasifier. The fine is set aside to be used in any way. The object of the present invention is also to use the thin parts in a useful manner in which they contribute to the formation of a bed of carbon-containing material in the melting gasifier, thus making it possible to reduce the cost of loading the bituminous coal-containing material. According to the invention, the object is achieved, because after undergoing a drying operation, the charcoal and charcoal powder that is charged are mixed with bitumen in a hot state and subsequently made by cooling bricks, and the bricks thus formed they are charged to the melting gasifier in the cold state and in the melting gasifier are subjected to a shock or vibration heating. Surprisingly, it has been found that cough bricks thus produced exhibit excellent thermal stability, which still exceeds the thermal stability of the bituminous coal containing material. The bricks show a very slight disintegration due to the temperature shock action of the melting gasifier above about 1000 ° C. This is due to the properties of bitumen used as an agglutination agent, which melts rapidly at the indicated high temperature and thus causes a beneficial bridging effect between the carbon particles. What is essential here is that the bitumen does not develop gas at the indicated temperature and also retains its spongy consistency and binding power. From DE-A-24 07 780 it is known to load raw or mined coal bricks made from a mixture of in particular anthracite and / or non-bituminous fine coal or high-grade fine coal such as coal and bitumen filler. to high vacuum as a bonding agent, serving the bricks thus produced for the ignition, in domestic stoves, or optionally, if subjected to a thermal process such as oxidation, low temperature carburetion, or coke, being even suitable for loading a blow oven. However, these bricks meet different requirements than the bricks produced according to the invention, the most essential thing with the bricks of the present invention is the thermal stability, that is, the bricks should not explode even with sudden temperature shocks in the case of charging to a melting gasifier, insofar as according to DE-A-24 07 780 it is important that the bricks have a high stability, this is high resistance to pressure, to allow them to be loaded in the blowing furnace. According to the known method, the high vacuum bitumen is heated to 200 ° C and after mixing with the fine coal bricks are made at a temperature of about 85 ° C. Due to the high fraction of coke formers in the bricks A coke network is formed, which results in high stability. According to a preferred embodiment, the fine coal and coal dust are separated during and / or after the drying of the carbon-containing material being loaded and then treated in the hot state. The bituminous carbon containing material resulting in the separation of fine coal and coal dust according to a preferred embodiment of the method of the invention, is charged directly to the melting gasifier. Preferably fine carbon with a particle size less than or equal to 8 mm is separated from the carbon-containing material. EP-B-0315 825 discloses a method of the type initially described, in which the fine coal after grinding is mixed with a binder, for example lime, molasses, bitumen, or pitch, and granulated, after which is introduced in the melting gasifier. However, according to the invention, a granulation operation is not carried out but rather a brick formation, the bricks presenting a higher thermomechanical stability in comparison with the granulates. Another disadvantage that is presented according to EP-B 0315 825 is the considerable expenditure of energy to grind a fine carbon. According to the invention, this disadvantage is avoided because the carbon-containing material is not milled, but the fine coal and coal dust are separated. From AT-B-376 241, a method is known according to which the solids made of carbon as a powder which have left a melting gasifier by the reducing gas separate the reducing gas and agglomerate and the agglomerates thus formed, in particular formed coke, are recirculated to a melting gasifier. However, unlike the invention, the carbon-containing material that is charged does not agglomerate, and the fine carbon can not be loaded on a large scale. With the method in accordance with AT-B-376 241, another disadvantage arises because the binder medium is arranged directly after the hot cyclone serving to separate the carbon as a powder, which requires considerable expenses in terms of construction. According to the invention, the fine coal or coal dust separated from the coal-containing material that is charged is bitumen-mixed and bricks are made, the brick formation is disposed downstream of the drying of the coal-containing material. Thus, the heat content of the fine coal and coal dust after drying is suitable for use in mixing with the bitumen and the formation of the bricks. No additional energy is expended when making the bricks.

According to a preferred embodiment of the method, the fine carbon and the coal dust are mixed with bitumen at a temperature below 100 °, preferably at a temperature between 75 and 80 ° C. Advantageously, bitumen is charged with a softening point below 80 ° C, preferably below 75 ° C. Optionally it supplies additional heat during the mixing operation, to ensure the softening of the bitumen. According to a preferred embodiment of the method of the invention, up to 30% coke of. The oil is loaded as a material containing carbon, which as it shows insufficient thermal stability. The bricks obtained by proceeding according to the invention, however, show a sufficient degree of thermal stability. Preferably the material containing charcoal that is charged is dried at a residual moisture of less than 5%. According to a variant, the bricks of the bricks are separated from the bricks formed of fine coal and coal dust and recycled to the brick making process. The bricks, formed of charcoal and coal dust, are advantageously cooled to a lower temperature than ° C during and / or after making the bricks. These have a particularly high stability to temperature as a result, in particular, of shock heating when charged to the melting gasifier. According to the invention, there is a suitable charged carbon when it has an ash content of 10 to 25%. As a result of this, the method of the present invention is particularly characterized by great economic efficiency, so that even liquid metal obtained from partially or completely reduced minerals upon melting in the melting gasifier can be produced at a favorable cost, because it is charged to the melting gasifier, as initially described, the same material containing coal that is used to produce the bricks, which is presented as if it were a by-product, in the use of the fine particle portion of the coal-containing material. According to the invention, charcoal having volatile portions of between 18 and 35% is also charged. Here it is not necessary to use high grade coal. Preferably the fine coal and coal dust are mixed at the temperature at which they leave the drying of charcoal with bitumen of approximately the same temperature, where the temperature of the material to be mixed is suitably 70 to a maximum of 100 ° C, preferably 75 to 85 ° C, at the time of mixing. With this, a good bitumen bond is assured as well as economic control. In addition, the product formed of fine coal, coal dust and bitumen does not need to be cooled only slightly before becoming bricks.

Another advantage of the method of the present invention has to be seen in that the bitumen of the type normally used in the construction of roads in a given place, can be used as bitumen therefore there are no special requirements as regards bitumen. A plant for carrying out the method of the present invention comprises a melting gasifier, a feed duct for metal carriers, in particular for reduced or partially reduced iron sponge, which flows into the melting gasifier, oxygen supply ducts or gas containing oxygen and for carbon-containing material formed at least in part from fine coal and coal dust, a discharge pipe from the melting gasifier for a reducing gas formed in the melting gasifier, and a bypass for pig iron, and the slag provided in the melting gasifier being charged, downstream from which a mixer and subsequently to a medium for making cold bricks with fine coal and coal dust are connected, the cold brick making means being connected in flow with the gasifier. According to the preferred embodiment, * a separating means is provided to separate the fine carbon and the coal dust from the material containing carbon being loaded. According to another preferred modality, a feed duct is provided to load bituminous coal containing material directly to the melting gasifier. A steam generator is suitable to supply heat to the mixer. Between the cold brick making means and the melting gasifier, a means for separating the bricks from the bricks is preferably provided. The invention will now be described in greater detail with reference to the drawing, which illustrates a preferred embodiment of the invention. In figure 1 the reference number 1 indicates a melting gasifier to which sponge iron 3 is charged at least partially reduced via a feed pipe 2, which after the optional final reduction, melts in the melting gasifier 1, properly pass through a bed 4 of material containing carbon. The melting gasifier 1 is further provided with a supply duct 5 for oxygen or an oxygen-containing gas, with supply ducts 6a, 6b for coal-containing material, with a discharge pipe 7 for reduction gas generated in the melting gasifier 1 thus as with separate branches 8, 8a for molten pig iron 9 and molten slag 10, respectively. The carbon-containing material 11 that is charged is dried in a first drying medium 12. The carbon powder 13 that is produced is removed and subjected to further treatment in a second drying medium 14. The carbon-containing material is discharged from the first medium of drying 12 in a hot state, whose temperature is about 60 ° C, washing to a separating means 15, for example a sieve, and in the process, fine coal 16, is separated from the material containing bituminous coal of a certain size 17 For example, fine carbon 16 has a particle size equal to or less than 8 mm. The bituminous coal containing material 17 by means of the supply duct 6b is supplied directly to the melting gasifier 1. In contrast to this, the fine coal 16 passes into a storage vessel 18 and thence to a mixer 19 where the fine coal 16 it is mixed with bitumen 20 taken from bitumen tank 21. Charcoal powder 13 is also fed to mixer 19 from second drying means 14, which is stored intermediate in a coal storage hopper. energized 22. The mixer 19 is heated to about 75-80 ° C using steam produced in the steam generator 23. In this way it is ensured that the softening point of the supplied bitumen 20 is exceeded. But it is also possible that the calorific content of the fine carbon 16 will be sufficient to supply the thermal energy required to soften the bitumen 20, so that no additional energy is needed in the form of steam. The loaded bitumen 20 can be ordinary residual asphalt of the type used in road construction, with a softening point lower than 75 ° C, which is obtainable worldwide at a favorable cost, for example betumen of type B70 according to with ON0RM B 3610, having the following specifications: Softening point (ring and ball method) (ÓNORM C 9212): 47 - 54 ° C Needle Penetration at 25 ° C (ÓNORM C 92 14): 50 -80 mm x 10"1 The mixture of fine carbon 16, carbon powder 13 and bitumen 20 is subsequently made cold bricks using a means for making cold bricks 24, at a temperature of about 70 to 75 ° C, that is, no thermal energy is spent for the bricks The bricks 25 thus produced are finally supplied to a means 26 for separating the bricks of the bricks, which do not have the size required to be loaded in the melting gasifier 1, means 26 which at the same time serve as a cooling medium In the process the bricks 25 are cooled to a temperature of less than 30 ° C. The brick chips that do not have the size required to be charged to the melting gasifier 1 are recycled to the briquetting process.They first pass to a collecting vessel 27 from there to the storage vessel 18 for fine coal 16. The bricks 25 via the duct or supply 6a are supplied to the interior of the melting gasifier 1, from where they are subjected to a shock heating. Surprisingly, it has been found that the bricks exhibit an extremely high thermal stability which is even greater than the thermal stability of the bituminous coal containing material 17, as enunciated by the following example. South African and Australian mine coal were dried and screened according to the method of the invention where a bituminous coal and carbon dust and fine coal fraction were obtained. Coal dust and fine coal were made by applying bricks. the process for making bricks of the invention. The thermal stability of the bricks thus produced was then compared to the stability of the respective bituminous coal. The thermal stability was determined because a charge fraction with a particle size of 10 to 16 mm was subjected to a heat treatment after the heat treatment was screened. The portions with a particle size in excess of 10 mm and with particle size below 2 mm respectively, were weighed separately and had the expressed percentages of the amount charged. The results are shown in Table 1. Table 1 South African Coal of Australian Coal Mine Mine The higher the portion with a particle size in excess of 10 mm and the lower the portion with a particle size smaller than 2 mm, the greater the thermal stability. As is clearly visible from Table 1, the thermal stability of the bricks produced by the method of the invention was considerably greater than that of bituminous coal. By proceeding according to the invention, fine carbon bricks and coal dust are obtained which show a high thermal stability, to be loaded in a melting gasifier without further elaboration, where the disintegration of the bricks is very slight even with the impact action of melting gasifier temperatures of approximately 1000 ° C. This makes it feasible to charge fine coal and coal dust to a melting gasifier in an economical manner, properly so that bricks produced from fine coal and coal dust contribute to the formation of carbon carriers in the melting gasifier, thus allowing considerable savings in terms of the cost of the bituminous coal containing material. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (3)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1.- Method for the production of liquid metal, in particular liquid ingot iron or liquid steel pre-products, from metal carriers, in particular reduced or partially reduced sponge iron, in a melt gasifier in which with supply of carbon-containing material, at least partially formed of fine coal and coal dust and with oxygen supply or an oxygen-containing gas, the metal carriers they melt in a bed of the carbon-containing material with the simultaneous formation of a reducing gas, optionally after a fine preliminary reduction, characterized in that after being subjected to a drying operation, the fine carbon and the coal dust being charged are they mix with bitumen in a hot state and subsequently cold bricks are made, and the bricks thus form two are charged to the melting gasifier in the cold state and in the melting or melting gasifier are subjected to a shock heating.
2. 2. Method according to claim 1, characterized in that the fine coal and coal dust are separated during and / or after the drying of the carbon-containing material and the coal powder is charged and then treated in the hot state.
3. 3. Method according to claim 2, characterized in that the bituminous coal-containing material resulting from the separation of the fine coal and the coal dust is loaded directly into the melting gasifier. . Method according to claim 2 or 3, characterized in that the fine carbon with a particle size less than or equal to 8 mm is separated from the carbon-containing material. 5. - Method according to one or more of claims 1 to 4, characterized in that the fine carbon and the coal dust are mixed with the bitumen at a temperature below 100 °, preferably at a temperature between 75 and 80 °. C, 6. - Method according to one or more of claims 1 to 5, characterized in that bitumen is charged with a softening point below 80 ° C, preferably below 75 ° C. 7.- Method according to one or more of the claims 1 to 6, characterized in that during the mixing operation additional heat is added. 8. Method according to one or more of claims 1 to 7, characterized in that up to 30% of petroleum coke is charged as carbon-containing material. 9. - Method according to one or more of claims 1 to 8, characterized in that the carbon-containing material is dried to a residual moisture content below 5%. 10. Method according to one or more of claims 1 to 9, characterized in that the brick chips are separated from the bricks formed of fine coal and coal dust and recycled to the brick making process. 11. Method according to one or more of claims 1 to 10, characterized in that the bricks formed of fine coal and coal dust are cooled to a temperature lower than 30 ° C during and / or after the forming process. the bricks. 12. - Method according to one or more of claims 1 to 11, characterized in that the coal with an ash content of 10 to 25% is charged. 13. Method according to one or more of claims 1 to 12, characterized in that the carbon with volatile portions between 18 and 35% is charged. 14. Method according to one or more of claims 1 to 13, characterized in that the fine coal and the coal dust at the temperature at which they leave the cold drying are mixed with bitumen of a similar temperature. 15. Method according to claim 14, characterized in that the temperature of the material to be mixed is from 70 to a maximum of 100 ° C, preferably from 75 to 85 ° C, at the time of mixing. 16. Method according to one or more of claims 1 to 15, characterized in that the bitumen of the type normally used in road construction at a given location is used as the bitumen for the invention. 17. Plant for carrying out the method according to one or more of claims 1 to 16, comprising a melting gasifier, a feed duct for metal carriers, in particular for reduced or partially reduced foamed iron,. which flows into the melting gasifier, supply or supply ducts for oxygen or an oxygen-containing gas and for coal-containing material formed at least partially from fine coal and coal dust, a discharge duct that starts from the melting furnace for a reducing gas formed in the melting gasifier and a bypass for the pig iron and the slag provided in the melting gasifier, characterized in that drying means are provided for the drying of the coal-containing material, and that is being charged, to the media, downstream a mixer is connected to make fine carbon bricks * and coal dust, with the means to make cold coal connected to the flow with the gasifier. 18. Plant according to claim 17, characterized in that a separating means is provided for separating the fine coal and the coal dust from the material containing coal being loaded. 19. Plant according to claim 17 or 18, characterized in that a feeding duct is provided for loading material containing bituminous coal. directly to the melting gasifier. 20. Plant according to one or more of claims 17-19, characterized in that a steam generator is provided for heating the mixer. 21. Plant according to one or more of claims 17 to 20, characterized in that a means for separating the bricks or brick particles is provided between the cold brick making means and the melting gasifier.