Patent Application
20130305882
The subject matter of the invention is a titanium-containing molded or formed body, a method for its production and its use.
In particular, the subject matter of the invention is a titanium-containing molded body in the form, for example, of a briquette, pellet or pressed stone, a method for the production of the molded body and its use in metallurgical processes, in particular for introduction in melting vessels or vessels pertaining to primary, secondary and tertiary metallurgy.
The invention also describes a method for increasing the durability of the refractory brick linings, for reducing the nitrogen oxides and also the sulfur content, in particular in the iron analysis and in the waste gas, and for reducing the harmful recycling substances in the melting furnace or shaft furnace, in particular the cupola furnace, by using synthetic and/or natural titanium carriers.
Furthermore, a method of using titanium-containing molded bodies as slag-formers, slag-protection agents and alloying agents is described.
On account of the rising demands on the part of environmental protection when smelting metals, the manufacturer has to fall back on ever more expensive methods in order to reduce substances that load the environment.
This increases the costs of production and thus puts a burden on the economic efficiency of a method. Numerous concerns have therefore developed methods to solve this complicated problem of achieving the set object in the most economical manner possible. Inter alia even when smelting metals in order to reduce substances that load the environment methods that already exist, such as melting gasification of waste, are used. The melting gasification of waste is based on the application of metallurgical process technologies. As a result, the following advantages take effect:
In secondary metallurgy, inter alia ferrotitanium, ferrocarbon titanium and titanium aluminum from aluminothermic production are also used as the alloying agents. These alloying agents, in particular ferrotitanium, are very expensive. Analysis of the ferrotitanium reveals that it consists mainly of 20 to 75% by weight or more Ti, of 2 to 10% by weight or more Al+Al2O3, of 0.2 to 8% by weight or more Si and of 20 up to 65% by weight or more Fe. A ferrocarbon titanium can have, for example, the following composition of the main constituents: Ti: 30 to 40%; C: 5 to 8%; Si: 3 to 4%; Al: 1 to 2%; Mn: 0.5%. Titanium aluminum can have, for example, the following composition of the main constituents: Ti: 5 to 10% or 50 to 63%; Al: remainder.
Substitution of these alloying agents by means of less expensive materials would considerably increase the economic efficiency of steel production.
The main reason for using titanium in modern steels or cast iron is the stabilization of austenitic chromium/nickel/steels with respect to sensitivity to cracks and the refinement of graphite inclusions in cast iron.
As a result of the processes in secondary metallurgy that often last a very long time (up to more then 2 hours), the slag zones of the ladles or vessels are stressed to a very great extent by the slag thermodynamics or kinetics.
Premature stoppages and expensive repairs of the ladles are necessary.
The cupola furnace is a shaft furnace in which metals can be melted. As a rule, the cupola furnace is used to produce metals. In this connection, the shaft furnace is loaded from above with coke as the energy carrier, the charge substances and the additional substances. The charge substances are solid crude iron, recycling materials, sheet stacks and selected metal steel scrap depending on the aim of production. In order to adjust the Si content in the iron analysis and also to establish favorable flow properties of the slag, molded bodies of silicon carbide, gravel and limestone are used as additional substances. In order to remove the metal, the furnace must be tapped a little above its base. Following the tap there is a siphon which has two outlets. In this connection, the liquid slag is diverted through the upper one into a collecting container. The iron underneath the slag is pressed through the other one and can, for example, be directed into a lead-point furnace. The functioning of the siphon is only possible on account of a slight excess pressure in the shaft furnace.
Often, however, melting or shaft furnaces reach their limits so there is still the obligation to develop novel special technologies that are enhanced for the use of metallurgical waste.
In the case of all the methods known hitherto for the treatment of waste substances, however, there is still loading by metallurgical recycling materials, for example zinc, sodium, potassium, lead, copper, vanadium etc. The more waste substances there are to be disposed of, the greater is the content of these undesired substances. This results in particular in the durability of the refractory brick linings and aggregates being considerably reduced.
Thus, for example, in a shaft furnace operating according to the OxiCup method ready pressed pieces are used whose composition is of various waste substances, for example iron-containing dusts, reducing agents, slag-formers and binders. The purpose of this technology is to allow the smelting process that normally runs in the blast-furnace process to run in the individual pressed molded bodies themselves. Thus dust-like iron-oxide carriers, which occur again and again in all smelting processes, are processed in a better way. Without these technologies, the proportion of dusts that can be reused would be comparatively small so that another form of disposal harming the environment would be necessary.
All pressed pieces used up until now contain the above-mentioned harmful metallic recycling substances. In the case of the thermal treatment of such waste substances, moreover, a waste gas develops that additionally contains NOx (nitrogen oxides) and SO2 (sulfur dioxide). In particular in the case of the OxiCup method, zinc, lead, sodium and potassium are to be pointed out as recycling substances that are harmful.
Zinc, on account of its low melting and vaporization point which is only low, has the negative property that it builds up in the throat dust and during recycling is introduced again and again anew into the recycling process. Those zinc particles that come into contact with the refractory brick lining reduce its durability. There has been no fundamental possibility up until now of making the negative effects of zinc harmless apart from that of removing zinc from the siphon.
Lead, on account of its great specific weight, takes effect at the base of a shaft furnace, penetrates into the points of porosity of the brick lining, and there destroys the same.
Alkalis, such as sodium and potassium, on account of the need for an acidic slag for discharge from the furnace, hinder sulfur-removal from the crude iron which for its part requires a slag that is as alkaline as possible. The contrary demands hinder the blast-furnace process to a very great extent. Furthermore, alkalis act as fluxing agents for any refractory brick linings, this in turn affecting the economic efficiency in a very negative way.
The elements copper, chromium, nickel and vanadium dissolve almost completely in the liquid crude iron so that they cannot be removed either in the downstream steel-production process. Here as well, the measure of reducing the contents as far as possible in the run-up is also important.
In all shaft furnaces coke is used as an energy carrier. In this connection, coke contains as an impurity inter alfa in addition undesirable sulfur. As a result of the combustion of the coke the liquid iron absorbs a proportion of sulfur which acts in a disturbing manner for further processing. The iron must therefore be freed from sulfur in special plants pertaining to primary and/or secondary metallurgy in a very costly and elaborate manner.
An object of the invention is to overcome the disadvantages of the prior art and thereby in particular by means of the use of synthetic and/or natural titanium carriers reduce the contents of the above-described negative recycling or accompanying substances, if applicable the content of nitrogen and also sulfur in the iron, to curtail the formation of NOx in order therefore to improve the quality of the waste gas and in order thus to protect the environment.
A further object of the invention is to increase, if applicable at the same time, the durability of refractory brick linings and also aggregates.
A further object of the invention is to provide titanium-containing molded bodies as alloying agents in primary, secondary and tertiary metallurgy.
Surprisingly, these objects have been achieved by means of the features of the main claim.
In accordance with the invention, the titanium-containing molded bodies contain synthetic and/or natural titanium carriers. What are to be understood by titanium carriers in this connection are substances that contain the element titanium, for example as an element, as a compound and/or as a constituent of a salt. The synthetic and/or natural titanium carriers are mixed with the other substances in a homogeneous manner, if applicable with the addition of a binding agent, and subsequently processed by means of a shaping process, for example, to form agglomerated stones, briquettes, pellets or pressed stones. If necessary, the titanium-containing molded bodies are subsequently subjected to heat treatment. The treatment temperature lies at up to 1,500° C., preferably at 80° C. to 1,400° C.
In accordance with the invention, it is also possible to use titanium-containing molded bodies that mainly consist of titanium dioxide or its compounds.
The titanium-containing molded body in accordance with the invention contains 0.5 to 100, preferably 1 to 90, particularly preferably 1 to 80, especially preferably 3 to 70, in particular preferably 4 to 65, preferably 4 to 50, in particular preferably 5 to 30% by weight TiO2 (calculated from the total titanium content). This molded body is suitable in accordance with the invention in particular for use in melting and shaft furnaces in the field of primary, secondary and tertiary metallurgy.
Synthetic raw materials from the chemical industry are pelletized by means of various chemical binders or re-shaped in sintering processes to form chargeable titanium carriers and in the respective processes of secondary metallurgy charged into the liquid media such as metals or slags.
In cases in which the users' respective plant system has an adequate blow-in system, the synthetic titanium carriers can also be blown in as alloying agents.
The respective quantities are matched to the respective requirement and charge-make-up calculation.
The synthetic titanium carriers are dissolved in the liquid metals or slags and increase the respective titanium content depending on the requirement.
In accordance with the invention synthetic titanium carriers with contents of 10 to 100% by weight, of 25 to 35% by weight, of 45 to 65% by weight, of 70 to 90% by weight and also of 100% by weight, calculated as TiO2, are at one's disposal.
In cases in which the oxygen content of the TiO2 is disadvantageous (for example outside vacuum systems), synthetic titanium carriers on the basis of titanium carbonitride, titanium nitrides or titanium carbides can also be used. Flexibility exists depending on the requirement.
For loading melting or shaft furnaces it is advantageous if the raw materials are present in the form of molded bodies. Thus, for example silicon carbide is used in the form of briquettes for loading the cupola furnace. In accordance with the prior art, such molded bodies are also produced on the basis of charge substances that are to be disposed of industrially. Coal and coal sludge, silicon-carbide-containing residues, throat and steelworks dust and sludge and other substances can be used, for example, as industrial charge substances.
Throat and steelworks dusts as well as sludge are very ferrous, yet crude iron can only be obtained from them in an economical Manner if they are poured into the shaft furnace as agglomerated solid bodies. Methods have been developed for this with which the so-called agglomerated stones are produced from the dust with the aid of binding agents. Before the process of pressing the molded bodies, the respective charge substances that are to be disposed of and smelted are mixed with coal-based slag-formers, binding agents and reducing agents.
Titanium-containing materials, selected from natural titanium ores, titanium-dioxide-rich slags and also synthetic titanium-containing materials or mixtures of at least two of these materials are used for the production of the titanium-containing molded bodies in accordance with the invention.
The synthetic titanium-dioxide-containing materials are selected in accordance with the invention from the materials listed below or mixtures thereof:
The production of the titanium-containing molded bodies in accordance with the invention is effected by mixing and/or adding the natural titanium ores, for example ilmenite sand and/or Sorel slag, titanium-dioxide-rich slags and/or synthetic titanium-dioxide-containing materials.
If applicable, further materials, for example charge substances that are to be disposed of industrially and/or reducing agents, based, for example, on coal, such as silicon-carbide-containing residues, coal and coal sludge, throat and steelworks dust and sludge and other substances, can be added to these titanium-containing materials.
In order to produce the titanium-containing molded bodies in accordance with the invention, one or more of the above-mentioned fine-grained titanium-containing materials is/are added to the mixtures of the fine-grained charge substances before the shaping by pressing, briquetting or pelleting. The mixture thus obtained is pressed with the aid of binding agents to form the molded bodies in accordance with the invention. If necessary, the titanium-containing molded bodies are subsequently subjected to heat treatment. The treatment temperature lies at up to 1,500° C., preferably at 80° C. to 1,400° C.
The titanium ores and titanium-dioxide-rich slags used to produce the titanium-containing molded bodies in accordance with the invention contain 15 to 95, preferably 25 to 90% by weight TiO2 (calculated from the total titanium content). The titanium ores can be used in an unpurified form or after separation of impurities and also the gangue in order to produce the additional substance.
The synthetic titanium-containing materials used to produce the titanium-containing molded bodies in accordance with the invention contain 5 to 100, preferably 10 to 100, particularly preferably 20 to 100% by weight TiO2 (calculated from the total titanium content).
The subject matter of the invention is, furthermore:
With the present invention:
When these titanium-containing molded bodies in accordance with the invention are introduced into shaft furnaces, these molded bodies are heated during the metallurgical smelting process. The reducing agents that are present in the molded bodies reduce the oxidic components of the shaft furnace. This applies both to the iron oxides and to the titanium compounds previously mixed with the stone. In this connection, the reducing agents in the molded bodies given the presence of the natural titanium ores, such as ilmenite (titanium is present as iron titanate in ilmenite), are reduced in the first step to form reactive TiO2; subsequently, the final reduction of the TiO2-particles that are obtained to form CO and metallic titanium is effected.
This reaction is effected immediately in the case of the synthetic titanium carriers, since titanium is mainly present as titanium dioxide. The elements that are thus reduced to metallic titanium react in the last step to form extremely highly refractory titanium carbides, titanium nitrides and/or titanium carbonitrides. Furthermore, highly refractory compounds with aluminum, magnesium, calcium are formed, for example aluminum titanate, magnesium titanate and calcium titanate. Moreover, metal oxide spinels that contain titanium are also formed. Subsequently, the molded bodies react in the course of the smelting process and are dissolved with the formation of a fine iron-slag mixture. In this connection, the titanium carbides, titanium nitrides, titanium carbonitrides or metal titanates and spinels emulsified therein are deposited wherever the respective liquids come into contact with the refractory brick lining. When these ultra-fine particles are deposited on the surfaces that are to be protected, very refractory and relatively dense layers of titanium carbonitrides, metal titanates and also spinels are formed. These deposited layers can not only repair defective points, but also protect regions that are sound against the penetration of liquids, such as iron or slag, and thus clearly increase the durability. The protective effect extends in particular as well in the interior of a shaft furnace, for example within the tapping channels or siphon constructions.
When the titanium-containing molded bodies in accordance with the invention are used as slag-protection agents, as a result of the addition of the titanium carriers, preferably as a result of the addition of synthetic titanium carriers, to the various secondary/and tertiary slags of the iron and steel industry, the advance wear in the slag zone of the steel ladles can be clearly reduced or completely prevented.
This process is made possible by virtue of the fact that the [lacuna] to the liquid system by blowing in or by charging coarse-grained bundles of synthetic titanium carriers with the compounds of barium and/or calcium and/or aluminum and/or magnesium present in the slags form various highly refractive titanates.
Since the slags and metals are in motion to a great extent as a result of the metallurgical rinsing process, the titanium-containing slags permanently come into contact with the zone of the advance wear in the slag region of the ladles. The highly refractory barium-calcium-magnesium and/or aluminum titanates are then deposited on the respective contact faces and reduce or prevent the wear of this critical zone of a steel ladle.
The advantage of this variant of the protective function of the various titanium carriers lies in the fact that even with oxidizing systems the refractoriness of the refractory linings of melting vessels that are to be protected is increased by the respective titanates or titanium compounds.
The undesirable accompanying substances, for example zinc, lead, sodium, potassium etc., are bound by the use of titanium-containing carriers as metal titanates and can thus be removed from the shaft furnace as a constituent of the slag.
In a manner conditional on the catalytic activity of titanium dioxide and also the tendency of titanium to form titanium carbonitrides with nitrogen, on the one hand the resultant nitrogen oxides are reduced catalytically to form nitrogen and on the other hand the formation of high-temperature-resistant titanium nitride, titanium carbonitride and/or titanium oxynitride is promoted. This has the advantage that the harmful nitrogen oxides are removed from the waste gas.
In addition, the sulfur that is present in the iron forms with titanium various titanium sulfides that are then removed from the shaft furnace as a constituent of the slag.
Ilmenite and/or Sorel slag and/or rutile sand are preferably used as natural titanium carriers. Titanium compounds, in particular titanium dioxide, are used as synthetic titanium-dioxide-containing carriers. Moreover, in accordance with the invention it is possible to use residues from titanium-dioxide production, not only in accordance with the sulfate process, but also in accordance with the chloride process.
In accordance with the invention it is also possible to make use of titanium-dioxide-containing waste substances, such as catalysts from DENOX-plants and also from the chemical industry.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 058 416.3 | Dec 2006 | DE | national |
| 10 2007 047 809.9 | Nov 2007 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12516608 | May 2009 | US |
| Child | 13947647 | US |
